8 PLEIOCENE FOSSILS. 



of the anterior pair, and the hinder or inner half-row of the posterior pair of ambulacra, 

 and less so in the remaining half-rows ; the groove-yoked pairs of pores, also, are wider 

 apart than in the other species, and the open pores within the star-belt-field more numerous 

 and crowded, extending to the sexual centre. 



This species was discovered by Dr. Edmund Ravenel, in the Pleiocine bed on his planta- 

 tion, called the Grove, Cooper River, and distinguished by the foregoing name, it was 

 registered in his Catalogue without description. It is here described from the original 

 specimen, and is a large, beautiful and well-marked species, entirely distinct from any other 

 heretofore described. 



Plate II., Fig. 3. Upper surface, natural size. 



" 3a. Lower surface, natural size. 



" 3b. Altitude from behind, natural size. 



" 3c. Profile, natural size. 



" 3d. Magnified view of the minute granulations of the upper surface. All of the tu- 

 bercles have been broken, only leaving the outline of their bases. 



" 3e. View of some tubercles of the lower surface, with a portion of half the next-lying 

 ambulacrum, less highly magnified than 3d. 



" 3f. A tubercle of the lower surface, with the shield in which it is set, highly magni- 

 fied. Though imperfect, it discovers the peculiarities of the hnops in the genus 

 Amphidetus. 



Locality. The Grove, Cooper River, S. C. (J. McC.) 



BRISSUS.— Klein. 

 BRISSUS SPATIOSUS.— McCkady. 



Plate HI., Fig. 1, la, lb, lc. 

 Pericosmus spatiosus, Ravenel, Cat. Echin. Rec. and Foss. of So. Ca., p. 2. (1848.) 



Brissus maximus, Brisso ventricoso Cubense valde similis, sed probabiliter hurnilior ; et 

 basem magis circularis / Ambulacro impart in fosso profundo et lato depresso ; Ambulacris 

 alteris infossis, quam speciei Cubensis minus profundis, sitis • Infra — sterno lato — Uhdique 

 Tuber cutis numerosis frequentibus, et parvis, clavatus. 



A very large Briscus very similar to the B. ventricosus of Cuba, but probably of less 

 height, and more circular in the outline of its base. The odd ambulacrum is set in a broad 



