EOCENE ECHINODERMATA. 119 



Subclass IRREGULARIA. 



Order GNATHOSTOMATA. 



Suborder CLYPEASTRINA. 



Family FIBULARIIDiE. 



Genus ECHINOCYAMUS Phelsum. 



Echinocyamus partus Emmons. 



Echinocyamus parvus Emmons, 1858, Agriculture Eastern Counties: North Carolina Geol. Survey Rept., p. 307, fig. 244. 

 Echinocyamus parvus Conrad, 1S66, Smithsonian Misc. Coll., vol. 7 (200), p. 31. 

 Echinocyamus parvus Heilprin, 18S4, Contrib. Tertiary Geology U. S., p. 17. 

 Echinocyamus parvus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 698. 



Description and determinative characters. — The location of Emmons's type of this little 

 echinoid is unknown, and the writer has been unable to find any specimen similar to it in the 

 North Carolina material studied. The description of Emmons is therefore quoted' in full, as 

 follows : 



Test small, oval, with rounded sides, avenues dorsal; mouth subcentral, rounded, large, with a crenulated margin; 

 vent between themouth and hinder margin; genital pores apparently four. The mouth is large in proportion to the size 

 of the body and the vent is situated halfway between the mouth and the margin. 



Dimensions. — Emmons's figure, which he states is natural size, is 5 milhmeters in length and 

 3 milhmeters in width. 



Related forms. — E. parvus is closely allied to E. huxleyanus. The latter apparently differs, 

 however, in being more pointed anteriorly and in having the periproct near the posterior margin. 

 E. parvus is also closely related to E. vaughani and E. texanus, which are to be distinguished by 

 having the periproct nearer the peristome. 



Locality. — Craven County, N. C. (Emmons). 



Geologic horizon. — Eocene (Emmons) . Very probably from the Trent marl. 



Echinocyamus huxleyanus Meyer. 

 Plate LVII, figures la-d. 



Echinocyamus huxleyanus Meyer, 1886, Alabama Geol. Survey Bull. 1, p. 85, PI. Ill, fig. 23. 

 Echinocyamus huxleyanus De Gregorio, 1890, Mon. faune eocenique Alabama, p. 251, PI. XLIII, fig. 15. 

 Echinocyamus huxleyanus Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 697. 



Determinative characters. — Test thin-walled and fragile, very small, flattened egg-shaped, 

 anterior end pointed. Upper surface low, convex; under surface concave around peristome. 

 Apical system excentric anteriorly, with four large genital pores. Petals rudimentary, open at 

 ends; pores not conjugated. Peristome central, relatively large. Periproct small, about one- 

 fourth the distance from margin to peristome. Tubercles relatively large. 



Dimensions. — Length 3 to 5 milhmeters; width 2 to 3 milhmeters; height 1 to 2 milhmeters. 



Description. — This httle Echinocyamus is found in some abundance in the sands of the 

 Claiborne group in Alabama. The test is notably thin-walled and fragile, in strong contrast 

 with the other American representatives of the genus. In marginal outline it is subelliptical to 

 elongate subovate and in general form subelhpsoidal to flattened egg-shaped; the anterior end 

 being more or less pointed, and the height being about hah or less than hah of the width. The 

 upper surface is low and gently convex; the lower surface flattened, slightly concave close to the 

 peristome. 



The ambulacral petals are rudimentary, extending two-thirds or more of the way to the 

 margin, open at the ends; poriferous zones nearly straight, pores round, pairs not conjugated. 

 The apical system is excentric anteriorby, with four large genital pores set close together, the 

 anterior pair being only slightly nearer together than the posterior pair. 



