156 



MANUAL OF. ZOOLOGY. 



in past geological epochs— the body is composed of a series or 

 calcareous plates, united together so as to form a cup or 

 " calyx," the bottom of which is continued mto a " column,' or 



pedicle, composed of a series 

 of calcareous joints or articu- 

 lations, whereby the animal 

 is fixed to some foreign body. 

 The upper part of the calyx 

 is roofed over by a series of 

 calcareous plates, and is per- 

 forated by the apertures of 

 the mouth and anus, the lat- 

 ter being sometimes absent. 

 In the recent species the 

 mouth is central, and there 

 is a distinct anus at one 

 side. The margin of the 

 calyx gives origin to the arms, 

 which are grooved on their 

 upper (or ventral) surfaces for 

 the ambulacra. In the liv- 

 ing Crinoids the ambulacral 

 grooves are continued along 

 the upper surface of the ca- 

 lyx to the mouth. In, the 

 PalseoEoic Crinoids there is 

 only a single opening on the 

 upper surface of the calyx, 

 which is sometimes central 

 and sometimes lateral, and 

 which serves both as a mouth 

 and anus. In many cases 

 this aperture is level with the 

 surface of the cal)fx, but in 

 many species it is placed at 

 the summit of a long pro- 

 jecting tube, which is termed 

 the "proboscis." The am- 

 bulacral grooves in the Palae- 

 ozoic Crinoids are found on 

 the ventral surfaces of the arms, as in the living species ; but 

 instead of being continued over the surface of the body to 

 the mouth, they stop short at the bases of the arms, where they, 

 gain access to the interior of the calyx by a series of specijil 

 apertures, — (Billings.) 



(1 



Fig. 44. — Crinoidea: Rkizocrinns Lofoien- 

 sis, a. living Crinoid (after Wyville I'honi- 

 son), four times the natural size. ~ "^^ 

 6 Calyx, c c Arms. 



a Stem. 



