NO. II ECHINODERMS — CLARK 3 



OPHIACTIS SAVIGNYI (Miiller and Troschel) 



Localities. — Clipperton Island ; shore collecting on rocks south of 

 landing place; July 21, 1938. Five specimens, all with 6 arms, taken 

 with Ophiocomclla parva (U.S.N.M. no. E.5631). 



Galapagos Islands : Sulivan Bay, James Island ; shore and tide-pool 

 collecting; July 24, 1938. One specimen with 6 arms (U.S.N.M. no. 

 E.5627). 



Galapagos Islands : Narborough Island ; shore collecting ; July 25, 

 1938. One specimen with 6 arms, taken with Ophiocomclla schmitti 

 (U.S.N.M. no. E.5641). 



OPHIOTHRIX ORSTEDII Liitken 



Locality. — Old Providence Island, 120 miles east of the Mosquito 

 Coast (lat. I3°2i' N., long. 8i°22 y W.); shore; reef and tide-pool 

 collecting; August 1. 1938. Three specimens (U.S.N.M. no. E.5615). 



OPHIOTHRIX GALAPAGENSIS Liitken and Mortensen 

 Plate 1, figs. 5, 6 



Localities. — Galapagos Islands : Sulivan Bay, James Island ; shore 

 and tide-pool collecting; July 24, 1938. Ten specimens (U.S.N.M. 

 nos. E.5613, E.5614, E.5630). 



Galapagos Islands : Elizabeth Bay, Albemarle Island ; south end of 

 the black beach north of the mangroves north of the two "red" 

 islands; July 26, 1938. Nine specimens (U.S.N.M. no. E.5642). 



Xotes. — In the specimens from James Island the disk is from 2.3 

 to 1 1.2 mm. in diameter, and the arms are from about 7 to about 55 

 mm. long. 



In the specimen with the disk 2.3 mm. in diameter the central 

 portion of the disk is occupied by a large circular central plate that is 

 bare except for 5 stumps ending in 3 long divergent points inter- 

 radially placed near the periphery. The exposed portion of the 

 radials is relatively smaller than in larger examples, the radial shields 

 extending only about half way from the periphery of the disk to the 

 center, and each radial shield bears 5-8 stumps with triradiate ends 

 resembling those borne on the small plates covering the remainder of 

 the disk. At the base of the arm there are 6 arm spines, the number 

 soon falling to 5 and later to 4 ; on the third and following arm combs 

 the lowest spine is in the form of a hook, these hooked spines 

 becoming very large in the outer portion of the arms. 



