May, 1909. New Echinoids — Slocom. 5 



DESCRIPTION OF GENERA AND SPECIES. 



Order SPATANGOIDA. 



Family CASSIDULIDiE. 



Genus CASSIDULUS Lamarck 1801. 



Test small, oblong, depressed, broadest posteriorly, longer than 

 broad, broader than high, convex dorsally, flat or concave ven- 

 trally. 



Apical system eccentric in front or subcentral; four perforated 

 genital plates; the madreporite passing back and separating the 

 postero-lateral genitals but not the radial plates. Ambulacral areas 

 subsimilar, short, flush, subpetaloid, not closing; pores continued 

 from the petaloid part to the floscelle, which is well developed. Ten- 

 tacles both simple and branchial (heteropodous) . Peristome eccentric 

 in front, the bourrelets narrow and strong, the phyllodes in grooves, 

 One peristomal plate to each interradium. Usually a median band 

 behind the peristome where there are no tubercles and where the test 

 is either cribriform, pitted or plain, or it may be absent. Periproct 

 supramarginal, in a depression or at the commencement of a groove, 

 elongated longitudinally. Tubercles small and very close together 

 on the dorsal surface, large and separated on the ventral, except on 

 the longitudinal median area. 



Range Cretaceous and Eocene. 



Cassidulus Subquadratus Conrad. 



i860. C. subquadratus Conrad, Jour. Acad. Nat. Sci. Phil., 2nd ser. 



Vol. 4, p. 291, pi. 47, fig. 19. 

 1 89 1 C. subquadratus Clark, Johns Hopkins Univ. Circ. No. 87, 



p. 76. 

 1893 C- subquadratus Clark, Bull. U. S. G. S. No. 97, p. 70, pi. 



31, fig. 1 a-h. 

 Original description: " Suborbicular, flat beneath, flexuous pos- 

 teriorly; lateral and end slopes truncated; anus very large, obtusely 

 ovate, with a depression beneath, extending to the margin, which at 

 that point is salient; ambulacra lanceolate. 



Length 3^ inches; Diameter 2% inches; Height 1% inches. 

 Locality. Tippah county, Mississippi." Clark gives Holly 

 Springs as the locality of this species. 



