226 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Primaries stouter (thickness about 4.5 per cent of length) ; a distinct 

 triangular impression on inner surface of valves of large pedi- 

 cellariae above hypophysis ; test, secondaries, and collar of 



primaries deep, dark brown misakiensis 



Abactinal system .35-45 h. d. ; primaries very long and slender, 2.5-4 h. d. 



(thickness only 2-3 per cent of length) ; very nearly smooth (slip 



easily between thumb and finger). 



Large pedicellariae always with 3 valves, which are distinctly pointed ; 



anal system about .50 of abactinal ; median ambulacral area about 



.37 of ambulacrum ; size small, under 35 mm. h. d. ; color pale, and 



primaries very white and shining cobosi 



Large pedicellariae very variable, sometimes with only 2 or with 4 

 valves, which are usually broad and are rounded at tip; anal sys- 

 tem about .45 of abactinal ; median ambulacral area about .50 of 

 ambulacrum; size large, up to 85 mm. h. d. ; color usually very 

 dark and primaries yellowish variabilis 



Porocidaris purpurata. 



Porocidaris purpurata Wyville Thomson, 1872, Ann. Mag. Nat. Hist., (4) 10, p. 302. 



Plate 59, Porcupine Ech., WyvilJe Thompson, 1875. 



One needs only to compare a specimen of this cidaroid with any other member 

 of the genus to reject Mortensen's ( :03) proposed genus " Histocidaris," for 

 aside from the pedicellariae, the only feature in which purpurata differs noticeably 

 from the others is the presence of an exceptionally wide collar on some of the 

 primaries of some specimens, and that can hardly be considered a very useful 

 character. Moreover Mortensen's proposed variety talismani, which he thinks 

 may even be a distinct species, cannot be recognized, for the primaries with 

 swollen, fusiform, violet collars occur in typical purpurata, and one is figured by 

 Thomson ('75), though they are not present in all specimens. The small spines 

 and some of the abactinal primaries are light reddish- or purplish-brown. The 

 largest recorded specimen is 50 mm. h. d. This species is known only from 

 the North Atlantic, save for the specimen from the Nicobar Islands, collected by 

 the " Valdivia," and referred to purpurata by Doderlein. 



Porocidaris sharreri. 



Porocidaris Sharreri A. Agassiz, 1880, Bull. M. C. Z., 8, p. 71. 



Plate 3, Blake Ech., A. Agassiz, 1883. 



This handsome West Indian species was dredged by the " Blake " off Georgia 

 in 279 ftlis. (in company with St. ingolfiana ) and also near Barbados in 35G fths. 

 The general color is red-brown and not at all purplish. The largest specimen is 

 69 mm. h. d., with spines 114 mm. long. 



