PERIPATAGUS. 139 



Key to the Genera of Palaeopneustidae. 

 No subanal fasciole. 



Periproct distinctly on dorsal surface Genicopatagus. 



Periproct not on dorsal surface. 



Labium (i. e. a distinct lower or posterior lip) and phyllodes wanting; a 



complete marginal fasciole present Peripatagus. 



Labium and phyllodes well developed. 



Ambulacra scarcely petaloid; pedicels much reduced. 



Test more or less depressed with apex not markedly posterior . . Phryssocystis. 

 Test high posteriorly where apex and abactinal system are placed. Delopatagus. 

 Ambulacra more or less petaloid. 



Interporiferous areas of petals well developed or at least evident. 

 Actinal ambulacra coarsely tuberculated like the interam- 



bulacra; mouth little excentric anteriorly Archaeopneustes. 



Actinal ambulacra more or less bare with no large tubercles; 

 mouth markedly anterior. 



Test high; v. d. much more than half length .... Palaeopneustes. 

 Test flattened; v. d. much less than half length 



Palaeotropus josephinae, adult. 



Interporiferous area of petals practically wanting Plesiozonus. 



Subanal fasciole present. 



No large primary tubercles with deeply sunken scrobicules. 

 No peripetalous fasciole. 



Subanal fasciole more than twice as wide as long Argopatagus. 



Subanal fasciole not twice as wide as long. 



Posterior ambulacra dorsally subpetaloid, much wider than ante- 

 rior pair Nacospatangus. 



No ambulacra at all petaloid Palaeotropus. 



Peripetalous fasciole present Pycnolampas. 



Some large primary tubercles with deeply sunken scrobicules in dorsal interambu- 



lacra Homolampas. 



Genicopatagus. 



A. Agassiz, 1879. Proc. Amer. Acad., 14, p. 210. 

 Type, Genicopatagus affinis A. Agassiz, 1879. hoc. cit. 



This is a monotypic genus which has not been met with since the Chal- 

 lenger collected specimens at a depth of 1950 fms. in the Antarctic Ocean. 

 I have never seen one so can add nothing to our knowledge of the genus. 



Peripatagus. 



Koehler, 1896. Bull. Soc. Zool. France, 20, p. 231. 

 Type, Peripatagus cinctus Koehler, 1896. Loc. cit. 



This is another monotypic genus of which I have seen no specimens. It 

 was taken by the Princess-Alice in 489-830 fms. in the eastern Atlantic. 



