228 Annals of the South African Museum. 



group, while the other two are also apparently endemic species of 

 East Indian geneni. 



The three littoral species are of particular interest in connection 

 with questions of geographical distribution. One ( Cominia occidental is] 

 is a peculiar, endemic species of a genus known otherwise only from 

 Korea Strait in 170 fms. while a second (Comanthus wahlbergii), also 

 endemic, finds its nearest relative in a South Australian species. 

 The third South African littoral comatulid is the wide-ranging Tro 

 piometra carinata, which occurs from Zanzibar, the Seychelles and 

 Mauritius, southward around the Cape of Good Hope and thence 

 northwestward to St. Helena, the coast of Brazil and the extreme 

 southeastern West Indies. The genus is otherwise distinctly East 

 Indian. 



It is evident therefore that the South African crinoid fauna is 

 essentially East Indian in its relationships and no doubt in its origin 

 also. The only exception is the Comanthus which is closely allied to 

 a species known only from southern Australia in shallow water. 

 This clearly hints at a common origin for the two and suggests 

 interesting speculations. 



In the following key to South African crinoids, 1 have used only 

 the simplest and most obvious characters. There are two reasons 

 for this: first, Mr. Austin Hobart Clark, in his most useful work on 

 the Crinoids of the Indian Ocean (1912, Echinoderma of the Indian 

 Museum, pt. 7) has given admirable keys to the families and genera 

 and it is therefore quite superfluous for me to repeat his work; 

 second, the South African species of Cominia is so unlike the Coman- 

 thus that it is not feasible to fit them into the same section of a brief, 

 artificial key and 1 have therefore ignored their family relationship. 

 Consequently the following key is absolutely artificial and does not 

 give the natural sequence of the species, a sequence which is followed 

 in the subsequent pages. The number of species involved is, however, 

 so small that little inconvenience will result from the inconsistency. 



Key to the South African Species of Crinoids. 



Stalk present. 



Only one or two short discoidal segments at top of stalk, immediately below 

 calyx ....... Bythocrinus chuni. 



More than a dozen short discoidal segments at top of stalk 



Monachocrinus coelus. 

 Stalk wanting (Comatulids). 



Arms 10 or more. 



Cirri numerous, 35 40. 



Cirrus segments few, 14 18 . . . Cominia occidentalis. 



Cirrus segments many, 30 36 . . Liparometra multicirra. 



