32 



NATURAL HISTORY BULLETIN 



with age or size, but is subject to very great individual diver- 

 sity. 



As this little echinoid is known not only from the West 

 Indian region but from the Hawaiian Islands and Dutch East 

 Indies as well as from the eastern Atlantic, it seems to have a 

 world wide distribution in the tropics. 



Station 54. Florida: 15 miles off American Shoal Light, 



about 130 fms. 2 specimens. 

 Station 57. Pourtales Plateau, 24° 18' N. x 81° 18' W., 200- 



225 fms. 7 specimens. 

 Station 64. Florida: about 8 miles off American Shoal Light, 



about 110 fms. 1 specimen 

 Locality unknown. 84 specimens. 



Grenocidaris maculata 



A. Agassiz, 1869. Bull. M. C. Z., I, p. 262. 1872, Rev. Ech., pi. VIII, figs. 

 1-18. 



This species occurs in abundance on Pourtales Plateau ("Nar- 

 rative" p. 174) and was also found on the Pentacrinus ground 

 near Havana (p. 83). The range of this little urchin is remark- 

 able, extending across the Atlantic and far into the Mediter- 

 ranean, and southward on the African coast to the region of the 

 Congo. The specimens in the Iowa collection are nearly all 

 from an unknown locality, presumably some station or stations 

 on the Pourtales Plateau. They range in size from 3 to 12 mm. 

 diameter. The growth changes between these two extremes 

 are not remarkable, the peristome decreasing only from 50 per 

 cent to about 45 per cent. Even in the largest the periproct 

 is practically all covered by the single suranal plate. The gen- 

 eral coloration is more or less light greenish abactinally, becom- 

 ing nearly pure white below. In some individuals, there is a 

 more or less elongated blotch of light purplish-brown, in each 

 interambulacrum near the abactinal system; this may extend 

 to the ambitus or there may be a second blotch at the ambitus. 

 In many individuals these, and other scattered blotches, are 

 distinctly green in tint. These blotches, from which the specific 

 name, maculata, arises are rarely absent even in very young 

 specimens. In the larger specimens, the basal part of aU the 



