]OURNAL OF PALEONTOLOGY, VOL. 23, NO. 1, PP. 84-86, PL. 22, ]ANUARY, 1949

TWO CRETACEOUS ECHINOIDS FROM PERU

c. WYTHE COOKEU. S. GeologicalSurvey,Washington,D. C.

ABSTRACT-Orthopsis titicacana and Hemiaster (Macraster) cascajalensis are de-scribed as new. The species from Brazil described by C. A. White in 1887 as Cot-taldia australis is transferred to Orthopsis.

Several collections recentiy made byNorman D. Newell (1946) from near thebase of the Ayavacas limestone member ofthe Moho formation west and northwest ofLake Titicaca in the Department of Puno,Peru, indude two species of echinoids rep-resenting different genera. Although one, aTetragramma, is not specifically identifiableand the other, an Orthopsis, is apparentiyundescribed, they throw some light on thecorrelation of the Ayavacas limestone, whichis usually regarded as Aptian and Albian.

The geologic range of both Tetragrammaand Orthopsis, as reported by Lambert andThiery (1910, pp. 187, 199), is Jurassic andCretaceous, but as both genera are the moreabundant in the Cretaceous, their occur-rence in Peru tends to corroborate the refer-ence of the Ayavacas limestone member ofthe Moho formation to the Cretaceous. How-ever, the genotype of Tetragramma comesfrom the Cenomanian and that of Orthopsisfrom the Senonian, and both genera at-tained their maximum proliferation in theCenomanian. So it may be suspected thatthe Ayavacas limestone is somewhat youngerthan Aptian.

The species of Tetragramma is representedby five individuals from Newell's locality104, north end of the bridge over Río Ilaveat Ilave. None of them are well enough pre-served for specific identification.

Orthopsis occurs at five localities, but ap-

paren tiy only one species is represen ted. 1tis most abundant at locality 159, a wellabout 4! kilometers east-southeast of Aya-vacas, from which 27 small individuals wereobtained. These juveniles might be mis-taken for a Cottaldia beca use of their nearlyspherical shape and speciously imperforatetuberdes, but their decoration is not thatcharacteristic of Cottaldia, and a few tuber-des retain the small perforated mamelonthat is characteristic of' Orthopsis,

The collection has been divided betweenthe American Museum of Natural Historyat New York, which retains the holotype,and the United States National Museum atWashington.

One nearly complete Hemiaster and twosiliceous crusts probably representing thesame species, all the property of the Insti-tuto Geologico del Perú, were placed in myhands for study by Dr. Newell. They werecollected at Cerro Cascajal, near Lima,Peru, from greenish limestone referred tothe Neocomian. Their.resemblance to Hemi-aster elegans Shumard (Cooke, 1946, p. 227),a species supposed to be restricted to de-posits of late Albian age, casts doubt onthis correlation.

ORTHOPSISTITICACANACooke, n. sp.Plate 22, figures 1-5

Subglobular, small, horizontal outiine cir-cular to subpentagonal. Apical system di-

EXPLANATIONOF PLATE 22

FlGs. 1-5-0rthopsis titicacana Cooke, n. sp. 1,2, Side and bottom of type, AMNH, X2; 3, paratype,USNM, X2; 4, details of surface, enlarged; 5, apical system, enlarged. (p. 84)

6-11-Hemiaster (Macraster) cascajalensis Cooke, n. sp., type. 6, 7, 9, Posterior end, side, andbottom, Xl; 8, apical system, enlarged; 10, top, X1.5; 11, top, X2, photographed underwater. (p. 85)

Drawings by Elinor Stromberg; photographs by Nelson A. Shupe except 11, which is by G. ArthurCoopero

84

]OURNAL OF PALEONTOLOGY, VOL. 23

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PLATE 22

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Cooke, Cretaceous Echinoids from Peru

TWO CRETACEOUS ECHINOIDS FROM PERU

cyclic, pentagonal. Ambulacral areas lessthan haIf as wide as the interambulacral;poriferouszonesforming a straight line fromocular plates to peristome, three zygoporesto each compound plate; interporiferouszones much wider than the zygopores, bear-ing one primary tubercle near the outer edgeof each compound plate, the tubercles form-ing two continuous rows adjacent to theporiferous zones. Interambulacral areaswide, each bearing one primary tuberclenear the middle of each plate and severalsmaller tubercles between it and the porifer-ous zones. Peristome small, less than haIf thetotal diameter, nearly circular, moderatelynotched. Periproct central, subcircular,rather large. Tubercles consisting of a lai-getumid boss surmounted by a very smallperforated mamelon, which is commonlynot preserved. Miliary areas scattered withgranules. Spines slender, acicular.

Height 5.1 mm., diameter 7.0 mm., diam-eter of peristome 2.8 mm., diameter of peri-proct 1.0 mm. One individual from locality19 measures 16 mm. in diameter; its peri-stome is 6.6 mm. across.

Comparisons .-Orthopsis titicacana appearsto agree in all generic features with Cidaritesmiliaris d'Archiac, the genotype of Orthop-sis Cotteau, 1863, as figured by Cotteau(1864, p. 558, pl. 1131). In decoration, how-ever, it more cIosely resembles Orthopsisovata (Coquand) from the Cenomanian ofAlgeria as figured by Cotteau (1864, pl.1132), but it is very much smaller and noneof its ocular plates touch the periproct.

The only other South American Orthopsisto which I have a reference is Orthopsisaustralis (White) (1887, p. 251, pl. 27, figs.13, 14), which was described as a Cottaldiabut which has plainly perforate tubercles.(Lambert and Thiery, 1910, p. 201, refer itto Hebertia.) This Brazilian species is muchmore depressed than the Peruvian O. titica-cana.

Two species of Orthopsis have been de-scribed from the Washita group of Texas,O. occidentalis Cragin and O. charltoni(Cragin) (Cooke, 1946, p. 214, pl. 31, figs.6, '7). Both of these species are more de-pressed than O. titicacana and O. occiden-talis has a much smaller peristome. O. charl-toni occurs in the Main Street limestone,which is probably of early Cenomanian age.

85

Occurrence.-Newell's locality 159, about4! km. east-southeast of Ayavacas, Depart-ment of Puno, Peru; 800 meters southeastof the summit of Cerro Tucurgachí, openwell at north side of Ayavacas-Urcunimuniroad (type and 26 other individuals). Lo-calities 17 and 19, 500 meters southwest ofcamp office, Pirín, Department of Puno (twoindividuals, each embedded in hard lime-stone). Locality 135, Cerro Conchacaní,highway cut on road to Moquegua, 7 km.southeast of Puno (one individual embeddedin limestone). Locality 13, 400 meters westof Aguallane School, near Pirín, Departmentof Puno (one slab of limestone containingseveral poorly preserved echinoids probablyrepresenting this species).

Geologic horizon.-Lower 2 meters ofAyavacas limestone member of the Mohoformation, probably of Cretaceous age.

Types.-Holotype, American Museum ofNatural History; paratypes, United StatesNational Museum.

HEMIASTER (MACRASTER) CASCA]ALENSISCooke, n. sp.

Plate 22, figures 6-11

Test cordate, moderately high, gentlyrounded below, truncated behind. Apicalsystem central; ocular plates large, lunate,perforated, the posterior plate wanting;right anterior and left posterior plates touch-ing all the other genital plates, the other twogenital plates separated by the madre-porite, which is almost central. Ambulacralareas petaliferous, petals open at the distalend, the anterior pair longer than the poste-rior pair and extending almost to the mar-gin; paired petals in shaIlow depressions,anterior unpaired petal in a deeper groove,which extends to the peristome, anteriorpaired petals diverging at an angle approxi-mating 108°, the posterior about 64°.Poriferous zones of anterior petal like theothers, the zygopores consisting of a longouter slot and an inner slot about half aslong as the outer and in line with it. Zygo-pores beyond the petals much smaIler andfarther apart, the pores commonly oval andforming an obtuse angle with each other,Peristome subpentagonal, rather large, thedistance from its center to the anteriorpart of the ambitus less than one-third ofthe totallength of the test. Periproct smaller

86 C. WYTHE COOKE

than the peristome, oval, higher than wide,situated well up on the posterior truncation,plainly visible fram above. Tubercles ratherfar apart except along the ambitus, 'Vherethey are more numerous. No bare fasciolediscernible.

Length 37.3 mm., width 34.6 mm., height20.1 mm.

Comparisons.-Hemiaster cascajalensismost closely resembles H. elegans washitae(Lambert) (Cooke, 1946, p. 229, pI. 33, figs.1-4) fram the Comanche Washita graup ofTexas, from which it differs in its slightlyshorter petals, less angular outline, and lesssteeply sloping posterior truncation. More-over, the two slot-shaped pores comprisingeach zygopore of its anterior petal arealigned, whereas those of H.washitae areslightly inclined with respect to each other.In general appearance it resembles H.whitei (Clark) (Cooke, 1946:p. 224, pI. 32,figs. 16, 17), whose outline is more rounded,posterior truncation steeper, and whoseanterior zygopores are not linear but con-sist of sharply inclined ovate pores separatedby a gran ule.

Occurrence.-Cerro Cascajal, near Lima,Peru.

Geologic horizon.-In greenish limestonereferred to the Neocomian. However, itsresemblance to Hemiaster elegans washitae,a species supposedto be restricted to beds ofupper Albian age, casts doubt on this corre-lation.

Type.-Instituto Geológico del Perú.Replicas in the United States NationalMuseum and the American Museum ofNatural History.

REFERENCES

COOKE, C. WYTHE, 1946, Comanche echinoids:Jour. Paleontology, vol. 20, no. 3, pp. 193-237,pis. 31-34. -

COTTEAU, G., 1861-1867, Echinides: Paléon-tologie fran~aise, Terrain crétacé, t. 7,892 pp.,pis. 1007-1204.

LAMBERT, JULES, and THIÉRY, P., 1909-1925,Essai de nomenclature raisonnée des échinides,605 pp., 15 pis.

NEwELL, NORMAND., 1946, Geological investi-gations around Lake Titicaca: Am. Jour. Sci.,vol. 244, pp. 357-366.

WHITE, C. A., 1887, Contribui~oesa paleontologiado Brazil: Mus. Nac. Rio de Janeiro Archivos.vol. 7, pp. 1-273, 28 pis.

PUBLISHED BY PERMISSION OF THE DIRECTOR, U. S. GEOLOGICAL SURVEY