62 
CRETACEOUS ECUIXODERMATA 
OriTirRA? CuNLiPFEi,* PI. VI I, Fig. 40. 
“ Part of the disc and arms of a very distinct species, appai’ently belonging to 
“ the typical genus Ophiura, and evidently allied to the Op)hmra serraia of Romer, a 
“ species found in the white chalk of Germany and England. The plates of the disc 
“ in the Indian fossil are larger than in any known species of the genus. The 
“ disc-shields at the bases of the rays are broadly oblong and somewhat triangular. 
“The scales of the centre of the arms are small and angular; the lateral scales 
“ are very large and oblong. The spines are not preserved, hut were probably short 
“ and obtuse. The figure represents the specimen of the natural size. It was 
“found by Mr. Cunliffe at Ycrdachellum.” 
Order. CRIUOIDEA. 
The Echinodermata included in the present division are, as regards external 
charactei’s, distinguished by a cup-like body, or calyx, which is composed of zones of 
calcareous plates, and, as a rule, it is dorsally attached by an articulated stem, and on 
the opposite end provided with articulated arms. The stem is either single, or with 
lateral appendages, and at the base variously branched, like the roots of a tree ; rarely 
it becomes lost in advanced age, or still more rarely is it altogether wanting, in 
which case the calyx is either quite free (Marsnpiles ) , or directly grown on to foreign 
substances fUolopusJ. The plates composing the lower portion of the calyx are not 
articulated, those of the upper occasionally or partially so; they include the internal 
organs, and the uj^per end has a hard or membranaceous cover, usually provideil 
with a single central or eccentric opening, Avhich often serves as oral and anal aper- 
ture at the same time. From this aperture generally extend furroAvs to the arms, 
continuing on the inner side of these to their dilferent branches ; they are lined Avith 
cilia, Avhich facilitate the access of Avater to the mouth. As a rule, there are five arms, 
or a multiple of the same number, rarely four, and still more rarely a larger or 
smaller number. 
Out of about 186 different genera of Crinoidea, only three — Fcntacrinus, Antedon 
or Comatitla, and Uolopns — occur living, while the greatest number is found fossil, and 
the majority of them are from palaeozoic and mesozoic deposits. Our knowledge of 
the structure and internal organisation of the Avhole group has been recently very 
considerably increased by the valuable researches of Dr. Carpenter and Prof. W. 
Thomson upon the recent Antedon (=Comatula), and there is little doubt but that 
moi'e extensive dredging operations aaIU materially add to the informatioii on this 
interesting branch of zoological science, as Ave already know from the reports 
Avliich haAm reached the public of Prof. Agassiz’s expedition in American waters. 
Count Pourtales has recently described several intei’esting species of Antedon from 
the American Avaters. 
B r on n divides the Crinoidea into — Is^, Cystklea ; 'ind, Costata ; and Zrd, Bra- 
ehlata. The last is the most numerous, and is separated into two natural groups : 
* Ophicoma Cunliffei apud d’Orbigny, Prod. 
( 122 ) 
