12 POROCIDARIS SHARRERI. 



from the fossil species, in the way of spines associated with their respects 

 ive tests. 



When alive these Echini were of a brilliant vermilion color. 



Amonc the specimens of D. Blakei there are a number without fan- 

 shaped radioles ; others, in which there were only one or two of the slightly 

 flattened radioles similar to those of Plate II. Fig. 5 ; others again, in which 

 there were a few radioles like those of Plate II. Fig. 7 ; and others, in which 

 a few of the fan-shaped radioles took the extraordinary development we find 

 figured in Plate I. 



Dorocidaris papillata a. Ag. 



For localities see Bull. M. C. Z., V., No. 9, p. 185, 1878 ; Bull. M. C. Z, VIII., No. 2, p. 70, 1880. 



On our coast this species has been found by the " Blake " as far north as 

 Lat. 32° 33' N., Long. 77° 30' W. Along the Florida reefs, in the Gulf of 

 Mexico, and along the West India Islands, it is the most common sea-urchin 

 found from about 100 to 300 fathoms. I have dredged it to a depth of 8412 

 fathoms off the Grenadines. 



* Porocidaris Skarreri A. Ac. 



Porocidaris Sharreri A. Ag. Bull. M. C. Z., VIII., No. 2, p. 71, 1880. 

 Nevis, Barbados, \-2-2-W, fathoms. 



PL III., PL IV. Figs. 1. 2. 



This species differs from its Atlantic congener, P. purpurata Wy. Th., in 

 having a comparatively larger number of ambulacral plates, — no less than 

 fifteen for the median interambulacral plates (PI. IV. Fig. 1 ) in the largest 

 specimen collected, while iii a specimen of P. purpurata of nearly the same 

 size there are only ten; the ambulacral granulation is also much finer, and 

 the large areolar ring of comparatively large granules is flanked by smaller 

 granules arranged in irregular lines parallel to the suture. We find no 

 such arrangement in the coarse granulation of the interambulacral plates 

 of P. purpurata. 



This is a larger species (PI. 111.) than either of the other recent ones thus 

 far known. The two largest specimens collected were males; a single small 

 female, measuring slightly over an inch in diameter, shows that in this 

 species, as in /'. elegans, the genital openings are placed within the genital 

 plates (PI. IV. Fig. 2 >. 



