NO. II ECHINODERMS CLARK 7 



The mouth shields in young Ophiocoma alexandri are broadly egg- 

 shaped and about as long as the greatest (distal) width ; in Ophioco- 

 mella parva they are rhombic with slightly rounded angles, and only 

 half again as long as the greatest (median) width. 



In young Ophiocoma alexandri the side mouth shields are widely 

 separated from each other instead of being almost or quite in contact 

 as in Ophiocomclla parva. 



Dr. Clark did not compare the specimen sent him with his specimens 

 of O. parva from Torres Strait, and the description of that species is 

 not sufficiently detailed to admit of accurate comparison. It is very 

 likely that the specimens herein identified as 0. parva in reality repre- 

 sent a different species ; if this should prove to be the case I would 

 suggest that that species be called Ophiocomella clippertoni. 



OPHIOCOMELLA CARIBBAEA, n. sp. 



Ophiocoma pitmila (part) A. H. Clark, Proc. U. S. Nat. Mus., vol. 86, 

 No. 3056, p. 451 (station 28, U.S.N.M. no. 5559), pi- 54, fig- 3, Apr. 5, 

 1939 (the type specimen). 



Description. — This species is very similar to 0. parva. In the type 

 specimen the disk is 4 mm. in diameter, and the 6 arms are about 13 

 mm. long. The 3 arms on one side are slightly larger than the 3 arms 

 on the opposite side. 



The plating on the aboral surface of the disk is somewhat coarser 

 than is the case in 0. parva, and the spinules are larger, less numerous, 

 and more scattered. There are about 50-60 spinules to each square 

 millimeter instead of about 100 as in 0. parva. The spinules are 

 mostly about twice as high as thick, or rather higher, swollen-conical 

 with usually rounded tips, and are separated from each other by sev- 

 eral times their basal diameter. 



The first tentacle pore has 2 tentacle scales instead of only a single 

 one as is usually the case in O. parva, but those following have only 1. 



The mouth papillae, especially the outermost, are slightly narrower 

 and less rounded than those of O. parva. 



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

 mouth shields. 



The central portion of the interbrachial areas below, as in 0. parva, 

 bears a few widely scattered spiniform granules. 



There are 4 arm spines until near the end of the arm, when the 

 number falls to 3. 



