306 bulletin: museum of comparative zoology. 



shallow water but it also occurs in crevices in rocks, in and among 

 corals, and in coralline Algae. Full-grown specimens, with disk 6 

 mm. across and arms 35-40 mm. long are relatively rare, the great 

 bulk of specimens collected having the disk only 2 or 3 mm. across. 

 The synonymy given above has been generally accepted of recent 

 years with two exceptions. Verrill has maintained that 0. krebsii is 

 distinct (but he has given no reasons for his belief) while 0. brocki has 

 not hitherto been considered identical with 0. samgnyi. A critical 

 examination of de Loriol's description leaves no doubt however that 

 his type was an adult of this species; the description of the upper 

 arm-plates is particularly convincing. As for 0. krebsii, I fully agree 

 with Koehler as to its identity with 0. savignyi. 



It is quite possible that the names in use for the West Indian species 

 of Ophiactis, 0. miilleri, and 0. savignyi, are not only not the first 

 names applied to the respective forms, but are not now used as Liitken 

 originally used them. Nothing whatever would be gained, however, 

 by an attempted readjustment. 



Ophiactis kroyeri. 



Liitken, 1856. Vid. med., p. 24. 1859. Add. ad hist. Oph., pt. 2, pi. 3, fig. 



8 a-c. 

 Ophiolepis atacamensis Philippi, 1860. Reise durch der wueste Atacama, p. 



190. 

 Ophiactis fragilis Ljungman, 1866. Ofv. Kongl. vet.-akad. Forh., 23, p. 164. 



The occurrence of this species along the western coast of South 

 America from Payta, Peru, to Talcahuano, Chile, and also at the 

 Hawaiian Islands is almost unbelievable, in view of the almost total 

 difference between the echinoderm faunas of the two regions. But 

 there is no doubt that the specimens on which 0. fragilis is based 

 and which were said to be from the Hawaiian Islands are identical 

 with South American specimens. If 0. kroyeri really occurs at the 

 Hawaiian Islands, it was probably introduced on the bottom of some 

 vessel. So far as I know, there are no recent records. 



Ophiactis simplex. 



Ophiolepis simplex Leconte, 1851. Proc. Acad. nat. sci. Phila., 6, p. 318. 

 Ophiactis oerstedii Ltitken, 1859. Add. ad. hist. Oph., pt. 2, p. 129. 

 Ophiactis simplex Liitken, 1859. Add. ad hist. Oph., pt. 2, p. 130. H. L. 

 Clark, 1915. Mem. M. C. Z., 25, pi. 10, fig. 5, 6. 



