440 BILLETIX: MISEUM OF COMPARATIVE ZOOLOGY. 



These specimens are adults, with disks 7-8 mm. across. The one 

 from Perico has the ground-color distinctly olive-green, while in the 

 other specimens it is very light brown. 



Panama: Perico Island. Tobaquilla Island. 



Three specimens. 



Ophionereis porrecta. 



Lyman, 1860. Proc. Boston soc. nat. hist., 7, p. 260. 1865. Illus. cat. 

 M. C. Z., no. 1, p. 147, fig. 14, 15. 



These specimens range from 3 to 9 mm. across the disk. 

 Paumotu Islands: Makemo. 

 Marshall Islands: Jaluit. 

 Three specimens. 



Ophiocomidae. 



Ophiocoma aethiops. 



Liitken, 1859. Add. ad hist. Oph., pt. 2, p. 141, 145. 



There are a dozen specimens of this well-known species from Perico 

 Island, Panama. 



Ophiocoma alexandri. 



Lyman, 1860. Proc. Boston soc. nat. hist., 7, p. 256. 



There are nine specimens of this species from Perico Island, Panama. 



Ophiocoma brevipes. 

 Peters, 1851. Monats. K.-Preus. akad. wiss. Berhn, p. 465. 



The species of Ophiocoma with two tentacle-scales and a very finely 

 granulated disk are \'ery perplexing. Whether we are dealing with 

 one, two, or three species is still uncertain. For the present, I think 

 it best to distinguish two species, 0. brevipes and 0. insularia, and 

 under the latter name, a typical form and a long-spined variety. 

 This, at least, is the division best adapted to the present collection. 

 The coloration of 0. brevipes is its conspicuous character and seems to 

 be quite constant; there is a ground-color of very pale yellowish 

 white with a distinctly greenish cast, and this is more or less marked 

 with l)i()tches and streaks of duskv or greenish; on the arms these 



