348 Yerrill, N'otes on Madiata. 



sides of America, being represented by numerous species. But with 

 the exception of one Mediterranean species, the genus is unknown 

 elsewhere, no representatives of it having been discovered in the 

 Indian or Pacific Oceans, wliere it appears to be replaced by Ophi- 

 opeza, Ophiarachna, etc., which have a similar appearance, but with 

 only ten ovarial openings, instead of twenty. Among other genera, 

 occurring on both coasts of America, but unknown in the great Indo- 

 Pacific Fauna, are the following : Ophiozona, Ophiostigma, Hemi- 

 pholis, Ophiop>hragmus, Ophiomyxa, Lytechinus, E)icop)e^ etc. The 

 following, although represented in other regions, appear to have their 

 greatest development upon the American coasts : Ophiactls^ Amphi- 

 ura., Echinaster, Luidla, Echviocldaris, Arhacia, MeU'ita. 



Several genera, which occur in the West Indies and appear to be 

 peculiar to the Atlantic, or have there their gi-eatest development, 

 have not yet been found in the Panamian Province. Such are, Pen- 

 tacrinus, Ophioblenna, Asteroporpa, Asterochetna, Clypeaster (also 

 Pacific), Cassididus, Plagionotus, 3Ioera* 



A few genera are found in the Panamian Fauna, which occur also 

 in the Indo-Pacific, but have not been met with in the Caribbean 

 Fauna. Among these are the following : Ojihiothela, Mithrodia, 

 Acanthaster, Astropyga, Metalia^ Lovenia. The following genera 

 seem at present peculiar to the Pacific coasts of America : Nidorellia, 

 Gymnasteria, ITeliaster, Echinodiadema., Echinoglycus (restricted), 

 Pygorhynchus (also fossil in Europe), Agassizia; and in the temper- 

 ate regions, Pycnopodia, Eoxechinus, Dendraster.\ 



There are, also, numerous species in each Fauna belonging to cos- 

 mopolitan genera, or to genera found in all tropical seas, but none of 

 these species, excepting the doubtful Holothurians, are common to both 

 coasts, or to the Panamian and Indo-Pacific Faunoe, or to the latter 

 and the Caribbean. Among cosmopolitan genera, represented on 

 each coast, are : Ophiolepis, Ophiocoraa, Amphiura, Ophiactis, 

 Ophionereis, OphiotJirix. Astrop>hyton, Astro2>ecten, Luidia, Aster- 

 iscus, Oreaster, Ophidiaster, Linckia, Gldarls, Dlddema, Psamyne- 

 chinus, Eahinometra, Toxopneustes, Stoloniclypeus, Prlssus, Meoma. 



From the preceding analysis of the genera, it is evident that while 

 the Panamian Fauna has several truly Indo-Pacific types, and some 

 that are peculiar, it is nevertheless most closely related to the Caiib- 



* Clypeaster speciosus V., and Moera chtho Mich., are now known from the west coast ; 

 Cassidultis is now regarded by A. Agassiz as the same genus with Pygorhynchus Paciji- 

 cus, and he refers Metalia nobilis to Plagionotus^ — Reprint. 



f Astridypeus (Japan), Pygorhynchus and Agassizia (W. Indies) must now be 

 omitted, — Reprint. 



