EOCENE ECHINODEBMATA. 143 



The ambulacral areas are petaloid, the petals rather long and narrow, converging toward 

 their extremities, where they remain partly open; the posterior pair longer than the rest and 

 bending outwardly near their extremities; the odd petal shorter than the posterior but slightly 

 longer than the anterior pair. The poriferous zones are rather narrow, but slightly more than 

 half the width of the narrow interporiferous areas; outer row of pores slitlike, inner row round: 

 pairs of pores conjugated by narrow grooves separated by low, easily effaced ridges. 



The interambulacral areas are broad; the posterior area slightly inflated from the apex to 

 the periproct, where it projects as an overhanging rostrum. The tubercles on the upper sides 

 of the test are numerous, unif ormly small, close together, and with deep scrobicules ; the inter- 

 vening spaces being covered with still smaller granulations. On the under side the tubercles are 

 larger, except along a rather wide, longitudinal, median band, which is free from tubercles but 

 dotted with numerous pits. 



The apical system is excentric anteriorly, compact, and consists of four basal plates per- 

 forated by large pores', the two anterior pores being slightly nearer together than the posterior; 

 five small radial plates, each perforated by a minute pore; and a large madreporite, which occupies 

 the center of the system. 



The peristome is of medium size, pentagonal, excentric anteriorly, directly beneath the 

 apical system, -with a well-defined floscelle. The floscelle is composed of five prominent rounded 

 bourrelets with granulated surfaces alternating with five large well-developed phyllodes. In 

 addition to outer rows of pores each phyllode has two inner rows ending in two rather large pores, 

 which are located just between adjacent bourrelets. 



The periproct is rather large, elliptical, transversely elongate, supramarginal, and con- 

 cealed beneath an overhanging rostrum at the head of a broad and rather shallow sulcus, which 

 extends beyond the rostrum to the truncated posterior margin of the test. 



Related forms. — C'assidulus raveneli from its size, shape, and details of structure is readily 

 separated from the other representatives of the genus occurring hi the American and European 

 Cenozoic deposits. In several features it resembles RhyncJiopygus calderi d'Archiac and Haime 

 from the Tertiary deposits of India, but it is more depressed and has a more regularly elliptical 

 marginal outline. In a less degree it resembles Eurhodia morrisii d'Archiac and Haime, also from 

 the Tertiary deposits of India, but it is more depressed and lacks the very elongated peristome so 

 characteristic of the Indian form. The nearest American form is Cassidulus depressus, from 

 which it is readily distinguished by its greater size and the details of its periproct. 



Localities. — South Carolina (Ravenel); Santee Canal (figured specimens), S. C; Eocky 

 Point and Wilmington, N. C. 



Geologic horizon. — In North Carolina in the Castle Hayne limestone, upper Eocene or 

 Oligocene. In South Carolina probably in the Cooper marl (upper Eocene) or the upper part 

 of the McBean formation (middle Eocene) . 



Collections. — American Museum of Natural History (A, B, and C); U. S. National 

 Museum; Johns Hopkins University. 



Cassidulus (Rhynchopygus ?) patelliformis (Bouve) . 

 Plate LXVI, figures 3 a-d. 



Catopygus patelliformis Bouve, 1851, Boston Soc. Nat. Hist. Proc., vol. 4, p. 2, text figures. 



Cassidulus patelliformis Desor, 185S, Synopsis des echinides fossiles, p. 290. 



Cassidulus patelliformis Bujardin and Hupe, 1862, Hist. nat. zoophytes echinodermes, p. 583. 



Cassidulus patelliformis Conrad, 1865, Acad. Nat. Sei. Philadelphia Proc., p. 75. 



Cassidulus patelliformis Conrad, 1866, Smithsonian Misc. Coll., vol. 7, p. 22. 



Cassidulus patelliformis Cotteau, 1888, Paleontologie franchise, Echinides Eocenes, vol. 1, p. 521. 



Cassidulus patelliformis Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 700. 



Determinative characters. — Test elliptical, narrowing and rather pointed posteriorly; upper 

 surface somewhat elevated, convex, elongate-subconical; under surface flat, meeting the upper 

 surface in an angular margin; apex slightly forward of the center. Ambulacral areas narrow, 

 petaloid; petals rather long, the anterior pair shorter than the posterior pair and odd petal 



