EOCENE ECHISTODERMATA. 117 



Subclass REGULAKIA ECTOBRANCHIATA. 



Order DIADEMOIDEA. 



Suborder ARBACINA. 



Family ARBACIID.E. 



Genus CCELOPLEtTRTJS Agassiz. 



CCELOPLEURUS INFULATUS (Morton). 



Plate LVI, figures la-i. 



Echinus infulatus Morton, 1833, Am. Jour. Sci., lstser., vol. 24, p. 131, PI. X, fig. 7. 

 Echinus infulatus Morton, 1834, Synopsis Organic Remains, p. 75, PI. X, fig. 7. 

 Echinus infulatus Morton, 1842, Acad. Nat. Sci. Philadelphia Jour., lstser., vol. 8, p. 217. 

 Echinus infulatus Bronn, 1848, Index palaeontologicus, vol. 1, p. 450; vol. 2, p. 187. 

 Echino-cidaris infulatus Ravenel, 1850, Am. Assoc. Adv. Sci. Proc, vol. 3, p. 160. 

 (?) Arbacia (?) sp. Bouv6, 1851, Boston Soc. Nat. Hist. Proc, vol. 4, p. 3. 

 Ccelopkunis infulatus Desor, 1858, Synopsis des echinides fossiles, p. 98. 

 Echinus infulatus Gabb, 1859, Cat. Invertebrate Fossils Cretaceous, p. 19. 

 Ccelopleurus depressus Conrad, 1865, Acad. Nat. Sci. Philadelphia Proc, vol. 23, p. 74. 

 Ccelopleurus infulatus Conrad, 1866, Check list, Eocene and Oligocene, p. 22. 

 Ccelopleurus depressus Conrad, 1866, Check list, Eocene and Oligocene, p. 22. 

 Ccelopleurus (Echinus) inflatus A. Agassiz, 1874, Revision of the Echini, p. 751. 

 Echinus infulatus ? Aldrich, 1886, Alabama Geol. Survey Bull. 1, p. 43. 

 Ccelopleurus infulatus Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 77. 

 Echinus infulatus Boyle, 1893, U. S. Geol. Survey Bull. 102, p. 118. 

 Ccelopleurus infulatus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 698. 

 Ccelopleurus depressus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 698. 



Determinative characters. — Test moderate, depressed. Ambulacra narrow, projecting on 

 upper surface, with two rows of tubercles extending from the peristome to the apical system, 

 plates compound except near apex; poriferous avenues narrow; pore pairs uniserial, in arcs. 

 Interambulacra broad, each with four rows of primary tubercles extending from the peristome 

 to slightly above the ambitus beyond which the inner rows disappear. Apical system laro-e, 

 the genital plates in contact. Peristome with small branchial incisions. Periproct large 

 subpentagonal. 



Dimensions. — Diameter 19.5 millimeters; height 10 millimeters. 



Description.— This, very characteristic species is represented by a single specimen from the 

 Santee marl member of the McBean formation of South Carolina. The test is of moderate 

 size, depressed and subpentagonal in outline. 



The ambulacra are narrow and project above the general level of the test. Each am- 

 bulacrum has two rows of primary tubercles that extend from the peristome nearly to the 

 apex. The tubercles are imperforate and noncrenulate. The plates are compound except 

 near the apex and consist of one primary and two demiplates. The poriferous avenues are 

 narrow, and the pore pairs which are uniserial are in arcs. 



The interambulacra are broad, each area being covered with four rows of primary tubercles 

 which extend from the peristome to a little above the ambitus, beyond which the two central 

 rows disappear, and the outside rows gradually decline in size to very small tubercles or even 

 into granules. The large bare median area produces a broad depression on the upper surface. 



The apical system is large, the genital plates coming into contact and separating the small 

 oculars. 



The peristome is large with small branchial incisions. The periproct is large and subpen- 

 tagonal in outline. 



Locality. — South Carolina (Morton). 



Geologic horizon. — Santee marl member of McBean formation, of Claiborne group, middle 

 Eocene. 



Collection,. — Academy of Natural Sciences of Philadelphia (1076). 



