NO. II ECHINODERMS — CLARK 5 



coast of Central America, and 0. valenciae from the east coast of 

 Africa and the Mascarene Islands. It is distinguished from this group 

 of species by the possession of 6 or 7 arms ; the occurrence on the disk 

 of short stout spinules with usually pointed ends instead of elongated 

 granules; by the occurrence of 2 tentacle scales (when present) 

 on the first tentacle pore only ; by the shape of the oral shields ; and 

 by the close approximation, or contact, of the adoral shields. The arm 

 spines in preserved specimens of the species of Ophiocomella almost 

 invariably stand out approximately at right angles to the arm, as in 

 Ophiactis. 



KEY TO THE SPECIES IN THE GENUS OPHIOCOMELLA 



a 1 . Spinules on upper surface of disk small and closely set, about 100 to each 



square millimeter (Torres Strait; Clipperton Island) . .parva H. L. Clark. 



a 2 . Spinules on upper surface of disk coarser and more scattered, not more than 



60 to each square millimeter 



b 1 . Spinules numerous, about 50-60 to each square millimeter, rather short 



and stout, mostly about twice as high as thick or rather lower, with 



usually rounded tips (West Indies) caribbaea, n. sp. 



b 2 . Spinules relatively few, about 30-35 to each square millimeter, longer and 

 more slender, mostly 3-4 times as long as thick with pointed ends 

 (Galapagos Islands) schmitti, n. sp. 



OPHIOCOMELLA PARVA (H. L. Clark) 



Plate 1, figs. 1, 2 



Locality. — Clipperton Island ; taken in shore collecting on rocks 

 south of the landing place; July 21, 1938. Forty-two specimens 

 (U.S.N.M. nos. E.5639, E.5640). 



Notes. — Of the 42 specimens collected, 39 have 6, and 3 have 7 

 arms. In the largest specimens the disk is 5 mm. in diameter and the 

 arms are 17 mm. long. 



In a number of specimens of different sizes the 3 arms on one side 

 are from slightly to much smaller than the 3 arms on the other side, 

 indicating that division takes place at various ages, and suggesting 

 that it may occur more than once. 



The radial shields are visible as small, narrow, elongate, widely 

 separated plates, one on either side of the arm bases. 



The first tentacle pore has usually a single tentacle scale, though in 

 each individual one or more of these pores have 2 tentacle scales. 



The adoral shields almost or quite meet beyond the inner end of the 

 mouth shields. 



