HORN SHELLS: Ceriths, Mud creepers & Telescope shells

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HORN SHELLS: Ceriths, Mud creepers & Telescope shells

The Families of Horn Shells: Cerithiidae J. Flemming, 1822 Horn shells or ceriths; Potamididae H. & A. Adams, 1854 Mud creepers & telescope shells The popular name horn shell is used for members of two families – Cerithiidae (horn shells or ceriths) and Potamididae (horn shells, mud creepers or telescope shells). The shells of both families are tall and tapering with many-whorled spires and are often strongly sculptured. The Cerithiidae have ovate, oblique apertures, the siphonal canal being short and recurved (turned upwards) or long and straight. The operculum is horny, thin and oval in shape. They are found in shallow, sandy marine habitats and are herbivorous, feeding on algae and detritus. The Potamididae usually have large apertures with short, twisted siphonal canals. The operculum is horny and circular. They are brackish water inhabitants and are to be found on muddy bottoms in mangroves and estuaries. They are herbivorous.

List of species

Family: 1. Cerithiidae J. Flemming, 1822 Ceriths 1. Cerithium citrinum G. B. Sowerby II, 1855 2. Cerithium rostratum A. Adams in G. B. Sowerby II, 1855 3. Cerithium zonatum (W. Wood, 1828) 4. Clypeomorus batillariaeformis Habe and Kosuge, 1966 5. Clypeomorus bifasciata (G. B. Sowerby II, 1855) 6. ‘Clypeomorus’ sp.1 7. Pseudovertagus nobilis (Reeve, 1855) 8. Rhinoclavis articulata (A. Adams & Reeve, 1850) 9. Rhinoclavis sinensis (Gmelin, 1791) Other species reported from Sri Lanka Cerithium echinatum Lamarck, 1822 Clypeomorus petrosa chemnitziana (Pilsbry, 1901) Pseudovertagus phylarchus (Iredale, 1929) Rhinoclavis sp. - Kirtisinghe, 1978 Rhinoclavis aspera (Linnaeus, 1758) - de Silva, 2006 Family: 2. Potamididae H. & A. Adams, 1854 Mud creepers, Telescope shells 1. Cerithidea quoyii (Hombron & Jacquinot, 1848) 2. Pirenella cingulata (Gmelin, 1791) 3. Pirenella conica (Blainville, 1829) 4. Telescopium telescopium (Linnaeus, 1758) 5. Terebralia palustris (Linnaeus, 1767)


Cerithiidae


Potamididae


Terebralia palustris: Upper row centre 79 mm - the common colour, dark brown; at right 99.3 mm - reddish-brown colour of specimen from Kalpitiya near lagoon shore; lower row - pale forms from white clay-bottom of an inland water body in Kaplitiya.


Cerithiidae Flemming, 1822

1. Cerithium citrinum Sowerby, 1855 Yellow cerith

Shell conical with tall tapering spire and pointed apex, the body whorl swollen. 10 whorls. Aperture a wide oval, oblique, a small anal

canal and a long straight angled anterior siphonal protuberance with an open canal.

29 – 33 mm high.

Two specimens with no collection data.

2. Cerithium rostratum A. Adams in G. B. Sowerby II, 1855 Beaked cerith

Shells with tall, pointed spires and many whorls. Suture constricted; sides of whorls rounded. Aperture oblique, oval. Outer lip

thickened, lirate within. Inner lip reflected, columella concave, smooth, a strong tooth guarding the anal canal, a short up-turned siphonal

canal. Varices present on every whorl. Sculpture of regularly placed, unaligned axial ribs crossed by spiral ridges of varying thickness raised

into nodules where they cross the ribs. Multiple threads in between the ridges.

24 x 11.26 to 30 x 11 mm (ht x w).

Kalpitiya, beached collection of 4 bleached and stained shells. No habitat data. Coll. ACM Niyas.

3. Cerithium zonatum (Wood, 1828) Zoned cerith [Clypeomorus zonatus Wood, 1828; many other synonyms]

Small shells with six-whorled, tapering pointed spires, oblique elliptical apertures with anal canals and angled siphonal canals. Colour

dark brown with white and russet bands and spiral lines, the white usually either side of the suture, low down on the body whorl and at the base. Appear to be variable as regards colour and pattern. Numerous recorded synonyms. Larger shells eroded and smoother, less eroded ones knobbly.

12.1 x 6.7 to 14.2 x 7.25 mm (ht x w); 16.46 x 7.8 mm dark chocolate-brown, no whit bands

Jaffna: Mandaitivu, in shallows 30 cm, underneath clam valves, and algae-covered intertidal rocky beach, exposed at low tide; Delft Island, intertidal rocky shore, amongst wet rocks, exposed at low tide.

4. Clypeomorus batillariaeformis Habe and Kosuge, 1966 Necklace cerith

Shell short, many-whorled spire pointed with scattered varices, a large one on the inflated body whorl. Aperture oblique; short anterior

siphonal and anal canals, the anterior canal turned 45 to the shell axis. Outer lip thickened, bevelled, lirate within. The columella concave,

two rounded swellings at both ends bordering the siphonal and anal canals, the posterior swelling stronger. Three rows of rounded nodules

encircle each whorl separated by one or two spiral threads; the body whorl has in addition 3 rows of granular threads below (the nodules

are not aligned to form axial ridges). Colour often obscured by encrustations but generally greyish with darker nodules. Interior white, the lip

edged with cinnamon spots or coloured cinnamon.

Found amongst intertidal mud and gravel and on shingle beaches. Many occupied by hermit crabs. Often coated with algal growths or calcareous encrustations, the sculpture eroded and obscured. Height about double the width. 20.9 x 11.68, 19.52 x 12.12, 18.3 x 10.3; 17.0 x 8.86; 16.68 x 9.25, 15.88 x 8.78 mm (ht x w)

Jaffna, Mandaitivu, intertidal shallows, rocky fringe of beach, abundant; Kalpitiya, Thihaliya, Puttalam lagoon western shore, mud bank of creek, empty. Trincomalee: Clappenberg Bay, CSAC beachfront, intertidal shingle beach; Cod Bay, Mud Cove, Intertidal rocks.

5. Clypeomorus bifasciata Sowerby, 1855 Banded cerith [Cerithium morus, in Apte, 1998; Clypeomorus morus (Lamarck, 1822) and many other

synonyms, including two subspecies - C. bifasciata bifasciata (Sowerby, 1855) &

C. bifasciata persica Houbrick, 1985]

Shell conical with straight sides, body whorl somewhat inflated. Suture simple. Covered with granular spiral threads of which some

are enlarged forming nodulose cords: three on each spire whorl, the body whorl with 4-5 additional rows. The nodules triangular, those on

the second row the largest - on the body whorl particularly so - followed by the third row and the uppermost row with the smallest. Outer lip

thickened, bevelled, crenulate with weak folds corresponding to the crenulations; no teeth. Varices present: on body whorl opposite the lip

and on earlier whorls. Columella concave, smooth apart from a nodule, being the end of an internal ridge, forming the parietal boundary of

the anal canal.

Ground colour white with spiral dashes of golden-brown, the nodules and larger granules tipped with grey. Interior white. Height a little

more than double the width.

Richmond, 1997 describes this as a “very variable shell, up to 3 cm, commonly with three granulated, spiral rows on each whorl (less pronounced towards the apex). Colour diverse, normally dark grey, brown or black with white highlights. Aperture pale or white, occasionally banded.”

26.8 x 13.24, 19.18 x 8.12, 18.4 x 8.44 mm (ht x w)

Jaffna, Mandaitivu beach, 30 cm deep shallows, underside of clam valves; intertidal rocky fringe of beach, abundant; Trincomalee,

Clappenberg Bay, CSAC, 0.5 m deep on silty sand near shore with light algal covering, live collected.


6. ‘Clypeomorus’ sp.1 Palatupana horn shell

An un-identified species that was thought to be a Clypeomorus but is more likely to be another genus such as Bittium.

Shell slender, conical, with tall pointed spire and rounded base. No varices. Aperture ovate, siphonal canal short, anal canal poorly developed. Columella concave, a weak swelling posteriorly. Outer lip thin with weak, irregular teeth. Encircled by oblique axial ridges

crossed by spiral grooves to form three rows of squarish, rounded nodules per whorl increasing in size downwards, separated by spiral threads. The body whorl has in addition 4 to 5 rows of granular threads below. Dark grey-brown, nodules white. Spiral threads banded brown/white; reddish-brown/white on the body whorl. Columella pale. Colour and sculpture obscured by algal or calcareous encrustations.

16.18 – 19.1 x 6.68 – 9.08 mm (range of heights and widths).

Kirinda, Palatupana Lewaya (seaward end of the saltern complex). Abundant on the muddy shore out of water and in the muddy

bottom of the shallows.

7. Pseudovertagus nobilis (Reeve, 1855) Noble vertagus [Cerithium nobile Reeve, 1855; Rhinoclavis nobilis (Reeve, 1855)]

Shell slender, tapering to a point, 15 whorls. Sides straight. Bent to apertural side. Aperture rounded, oblique, small but definite anal

canal, anterior siphonal canal short, recurved. Outer lip thin, inner lip reflected on to body whorl. No umbilicus. Whorls are encircled by flat spiral bands, lower ones overlapping the ones above, overlaid on the upper whorls by axial ribs that remain on lower whorls as tubercles on subsutural bands.

Pale buff coloured. Beach collections only, mostly faded, from the west coast. 38.8 x 11.27 mm, 31.88 x 10 mm, 32.0 x 9.14 mm (ht x w)

Wattala, Pegasus Reef Hotel beach, beached; Paiyagala beach, beached, rather faded but little buff colour remains.

8. Rhinoclavis articulata (A. Adams & Reeve, 1850) Many-grooved horn shell

Slender conical shell with straight sides. 13 whorls, apex pointed. Suture simple. Aperture oval. Outer lip swollen with thin edge,

varices present at irregular intervals on every whorl, inner lip reflexed onto body whorl, columella straight below, convex above ending in a

nodule at the margin of the short posterior anal canal. Anterior siphonal canal short, oblique. Sculpture consists of rows of rounded granules

separated by spiral grooves: the subsutural row distinctly large and rounded followed by 2 rows of transversely elongated low granules and

three rows with poorly formed granules. The body whorl has numerous rows of spiral ridges barely raised into granules irregularly. Colour

pale tan, the subsutural row paler, varices whitish, inner lip whitish.

22.39 x 6.98 mm (ht x w).

Kayankerny, Thennadi Bay, empty shell on muddy-sand bottom, 2-3 m deep.

9. Rhinoclavis sinensis (Gmelin, 1791) Knobbed horn shell [Cerithium obeliscus Bruguière, 1792]

Shell with a tall many-whorled pointed spire, oblique elliptical aperture with an anal canal and an upturned siphonal canal. The inner

lip reflected on to the lowest part of the body whorl, columella with two folds. Sculpture of spiral rows of granules, the uppermost row enlarged into pointed nodules. Operculum oval, thin, brown and horny. Upper surface of the shell may be encrusted and the nodules eroded, the underside usually clean. Whitish with brown dots on the spiral rows, the upper surface discoloured dirty grey; greenish in fresh

specimens coated with algae. On sand bottoms of intertidal rock pools and subtidal shallows amongst rocks. 29 – 62 mm high.

Galle, Unawatuna, intertidal rock pool, much encrusted, eroded; Weligama, Kapparatota, 1 m deep, in rock cavity; Tangalle, no collection data, encrusted; Kalkudah beach, beached.

Family Potamididae next page


Potamididae H. & A. Adams, 1854

1. Cerithidea quoyii (Hombron &Jacquinot, 1848) [Cerithium quoyii Hombron & Jacquinot, 1848; Cerithidea quadrata G. B. Sowerby II, 1866;

Cerithidea obtusa Lamarck, 1822]

Described from a single beached shell.

Conical shell with tall spire, 7 whorls, apex damaged. Suture constricted; sides of whorls convex. Aperture ovate, deep anterior

siphonal notch, anal canal guarded by a tooth. Outer lip thickened, coarse teeth inside. Columella smooth apart from posterio r tooth at anal

canal. Varices present, about two per whorl. Encircled throughout by spiral threads that cross axial ribs of varying thickness, the

intersections raised into nodules. The shell weathered and faded, patches of brown colour remaining.

19.36 x 8.42;20.38 x 10; 23.4 x 10.58 mm (ht x w).

Beached shell collected from Jaffna, Kachchativu Island by Devaka Weerakoon and Arjan Rajasuriya.

Reported by Pinto, 1986 from Negombo mangroves. Not seen by author in other areas, distribution appears to be restricted.

2. Pirenella cingulata (Gmelin, 1791) Girdled Horn Shell [Cerithidea cingulata (Gmelin, 1791); Cerithideopsilla cingulata]

Conical shells with tall spires, whorls flat-sided, sutures impressed, apices often eroded. Adult shells with a varix opposite the lip on

the body whorl, some with varix-like thickenings irregularly scattered. Shades of brown to grey, some suffused with red, the subsutural cord

often paler - white, yellow or tan, the anterior end pale with dark spiral lines. Interior whitish, the external pattern showing through.

Common, widely distributed, on mud flats of estuaries and lagoons, and shallow water. 25.74 x 9.2, 24.7 x 9.9, 20.0 x 8.25; 17.68 x 6.58, 14 x 6 mm.

Jaffna, Analaitivu Bay, intertidal muddy shingle beach, exposed at low tide, Jaffna, Delft island, intertidal rocky shore, rocks and sand, exposed at low tide; Mannar, abandoned fish culture ponds, mud bottoms; Kalpitiya, Puttalam Lagoon western shore, NARA Stn., intertidal mudflats & tide pools, 0.3-0.5 m deep, lagoon shallows on muddy sand; Puttalam, Karativu, Serakkuli, lagoon eastern shore, mud bottom of salt marsh

stream, in flowing water, near confluence with lagoon; Trincomalee, Cod Bay, Mud Cove, intertidal mud, exposed at low tide.

3. Pirenella conica (Blainville, 1829) Conical horn shell [Potamides conicus (Blainville, 1892)]

Slender conical shells with tall spires, the suture constricted. Whorls encircled by axial ribs separated from each other by wide

grooves to either side, crossed by shallow spiral grooves breaking them up into three rows of beaded cords. The beads transversely

elongated the uppermost row the largest and most distinct, the lower two rows sometimes hardly divided. Three to four spiral threads below

the beaded cords on the body whorl, only the uppermost visible on the spire whorls above the suture.

Generally brownish to greyish, sometimes with reddish tints, the uppermost row of beads white, the tops of other beads and the

threads whitish. These shells resemble C. cingulata but are slenderer, the spiral ornament rounded and elongated transversely.

Restricted distribution – salt marsh pond in Vanathavillu and shallow water of salt marsh in Mandaitivu Jaffna. One collection possibly

in Mannar or Delft Island, with no contemporary record.

21.34 x 7.3, 19.3 x 6.3; 18.6 x 5.9; 15 x 6.4, 12.2 x 4.5 mm.

Jaffna, Mandaitivu, salt marsh pool, Black and white patterns; Puttalam, Karativu, Serakkuli, salt marsh, shallow mud-bottomed pools

in marsh,

4. Telescopium telescopium (Linnaeus, 1758) Telescope Snail “Shell large, conical, with four straight-sided flat spiral cords per whorl. The base rather squared off. The columella twisted.

Operculum circular.” (Oliver, 1989) Interior purplish, upper whorls paler than lower. Operculum circular. The soft tissues coloured

emerald green (Houbrick, 1991 describes the soft tissues as greyish). Said to be edible.

Appears to have a restricted distribution – only one collection in Kayankerni. Unconfirmed observation on mudflats in Batticaloa and

Trincomalee.

This species was known only from a 53 mm high beach collection. A live colony was found at Kayankerni, on the muddy floor of a

partly dried-up mangrove. The much larger shells collected looked very different—they were gerontic.

Empty beached shells with no location data, Apices and lips damaged. Coll. Ananda Thenabadu

53 x 27; 53 x 27 mm.;

Kayankerni, on moist mud and leaf litter of dried up mangrove forest, live collected.

98 x 50; 97 x 41; 90 x 48; 89 x 39; 74 x 31 mm.

As the shells grow the apices tend to be eroded and so was the sculpture. Shells with the widest base were proportionately shorter and with

fewer whorls, as the following table shows:


74 x 31 mm: 15 whorls, 2 apical ones in the process of being lost. Basal 3 whorls covered with glossy periostracum, which was

progressively lost in the upper whorls, the uppermost whorls paler as a result of abrasion.

89 x 39 mm: 17 whorls, the apical 2 being lost. 4 whorls with periostracum, upper abraded, smooth, sculpture just discernible.

97 x 41 mm: 15 whorls, apical 2 being lost. Periostracum only on half of ultimate whorl, other whorls abraded with pale bands

below.

90 x 48 mm: 7 whorls, apex abraded smooth over lost whorls, periostracum absent, all whorls abraded smooth, sculpture

obliterated, uniform dark maroon/chocolate (no banding).

98 x 50 mm: 9 whorls, apex rounded. Periostracum present adjacent to aperture as a narrow band over most recently formed portion, absent elsewhere. Whorls smoothly abraded, uniform maroon/chocolate colour except pale apex.

5. Terebralia palustris (Linnaeus, 1767) Northern Mud Creeper

"Thick, heavy, conical shell with long pointed spire, up to 12cm. Whorls with strong axial ribs crossed by deeply incised spiral grooves.

Colour dark brown.” – Richmond, 1997.

Three deeply incised spiral grooves divide the whorls into four flat cords that are crossed by a series of axial ribs. The body whorl has

a low varix opposite the lip in adults. Immature shells do not possess the flared outer lip that the adults have. The columella is smooth and

pale, the siphonal canal very short. The circular operculum is thin, brown and horny with a central nucleus and many whorls. Colour

appears to depend on the substrate on which it lives: dark blackish-brown, lighter reddish-brown, cream with maroon and blue-grey

markings.

Common in mangrove waterways, on mud bottoms. Pale forms collected from the white clay bottom of Nachchiamman Genge, in

Kalpitiya. Three colour forms are illustrated—the common dark brown of those found in mangrove waterways; reddish-brown of one found

aestivating on dry land near the Puttalam lagoon; cream with dark markings of those collected from a white clay bottom. The colour of the

shell is likely to be dependent on the nature of the organic matter forming the substrate on which the animal lives (see quote below with

reference to P. cingulata..

“… but in some cases the overall dark brown colour appears to be the result of staining by organic-rich mud in mangrove

habitats; shells from cleaner and sandy habitats tend to be paler….” - Reid & Ozawa, 2016, p. 7 with reference to Pirenella

cingulata.

99.3 x 40 mm; 94 x 32 mm; 78.2 x 27.3; 72 - 46 mm immature shells.

Kalpitiya, NARA station, aestivating in undergrowth during dry spell; Kalpitiya, Nachchiamman Genge (a brackish water lake), on white clay bottom, pale forms and pale, pigmented in segments; Trincomalee, Kinniya, crab occupied in tidal pool; Trincomalee, Cod Bay, Mud

Cove, intertidal mudflat, mostly immature.

BIBLIOGRAPHY

Apte, Deepak (1998) The Book of Indian Shells, Bombay Natural History Society/Oxford University Press, Mumbai.

Abbott, R. Tucker (1994) Seashells of Southeast Asia, Graham Brash, Singapore.

De Bruyne, R. H. (2003) The Complete Encyclopedia of Shells, Rebo Productions, Lisse, The Netherlands.

de Silva, Darshani (2006) Current Status of Taxonomy and Ecology of Marine Molluscs in Sri Lanka. In: Bambaradeniya, Channa (Ed), The Fauna of Sri Lanka (2006), IUCN, 274-287.

Dey, Anirudha (2006) Handbook on Mangrove Associated Molluscs of Sundarbans. The Director, Zoological Survey of India, Kolkata.

Fernando, Malik (2009) Shells of the Sri Lanka Seashore, Biodiversity Secretariat, Ministry of Environment, Sri Lanka.

Houbrick R.S. (1991). Systematic review and functional morphology of the mangrove snails Terebralia and Telescopium (Potamididae; Prosobranchia). Malacologia. 33(1): 289-338., available online at https://www.biodiversitylibrary.org/item/47260#page/299/mode/1up

Oliver, A. P. H. (1989) The Hamlyn guide to shells of the world, Hamlyn, London.

Pinto, Leonard (1986) Mangroves of Sri Lanka, Natural Resources, Energy and Science Authority of Sri Lanka, Colombo.

Reid D.G. & Ozawa T. (2016). The genus Pirenella Gray, 1847 (= Cerithideopsilla Thiele, 1929) (Gastropoda: Potamididae) in the Indo-West Pacific region and Mediterranean Sea. Zootaxa. 4076(1): 1-91.

Richmond, M. (Ed.) (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean islands. Sida/Department for Research Cooperation, SAREC: Stockholm, Sweden. ISBN 91-630-4594-X. 448 pp

Subba Rao, NV & Dey, A (2000) Catalogue of Marine Molluscs of Andaman and Nicobar Islands, Rec. zool. Surv. India, Occ. Paper No. 187, i -x, 1-323 pp., Director, ZSI, Calcutta.

30.5.2019; 18.6.2020 - reviewed and completed.

HORN SHELLS: Ceriths, Mud creepers & Telescope shells

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