152 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



small, subquadrangular or lozenge-shaped; the others elongato- 

 lingulate, reaching half the height of the body ; the margins 

 subparallel. 

 The two regular radial plates are long, slender, deeply furcate, re- 

 ceiving the ambulacral areas. The lateral radial plates irregular, 

 having their ventral extremities similar to those of the regular 

 radials, and the dorsal extremities elongate triangular, and curved 

 to unite with the elongate basal and short dorso - radial plates. 

 Dorsal or short radial plate shield-shaped or irregularly subovate, 

 truncate and strongly angular at the top for the reception of the 

 summit-pseudambulacral field. Interradial plates minute. Four of 

 the pseudambulacral fields long and slender, extending about 

 four-fifths of the entire length of the body, as wide as the limbs 

 of the regular radial plates, composed of a double series of short 

 obliquely arranged and beautifully ornamented poral plates, 

 which number about sixteen to one-fourth of an inch. The fifth 

 pseudambulacral field small, triangular, horizontal at the sum- 

 mit of the body, composed of eight or ten curved plates on each 

 side. Each plate of the pseudambulacral field supports a long 

 slender arm or tentacle, composed of a double series of short 

 plates interlocking on the back. In the lower part, the breadth 

 from the back to the inner face is about three times the transverse 

 diameter, gradually decreasing in the extension upwards, and 

 becoming about equal to the transverse diameter : here they 

 appear to be grooved on the face, and marked with small scars as 

 if for the attachment of cilia. The arms have been preserved, in 

 some instances, to a length equal to two-thirds the length of the 

 body, and are yet imperfect at their distal ends. 



This species is the second of the genus that has been discovered. The 

 E. cassedayi of Shumard occurs in limestones of the age of the Upper 

 Helderberg rocks near Louisville, Kentucky; and the present species, in 

 the shales of the Hamilton group in Western New York. This differs from 

 the western species in having the long basal plate much narrower, the 

 short radial plate distinctly angular in the middle, and the pseudambula- 

 cral areas wider, while the entire width is proportionally less than in that 

 species. C. A. White, collector. 



GENUS CODASTER = CODONASTER ( M'Coy). 



CODASTER PYRAMIDATUS. /'ft^Cj J ^ ; ^ v 



The Codaster pyramidaius of Shumard, or a closely allied species, oc- 

 curs in the Upper Helderberg limestone, near Caledonia in Livingston 

 county, N.Y. July, 1862. 



