104 



INVERTEBRATE ANIMALS. 



numerous, both individually and in types, but they are rep- 

 resented at the present day by no more than three or four 



living forms, of which one 

 only (the feather-star) is at 

 all of common occurrence. 

 The body in the Crinoids con- 

 sists of a central disk or cup 

 formed of calcareous plates, 

 and protecting the body of 

 the animal. From the mar- 

 gins of this cup spring five 

 or more arms -which are ar- 

 ranged in a radiating manner, 

 so as to form a more or less 

 feathery crown. In one of 

 our living forms, the animal, 

 when full grown, is free ; but 

 in all other living genera, and 

 in the great majority of fossil 

 forms, the body was attached 

 throughout life to the sea- 

 bottom by means of a jointed 

 stalk attached to the lower 

 surface of the cup (Fig. 36), 

 thus somewhat resembling a 

 lily. 



The commonest living spe- 

 cies is the rosy feather-star 

 ( Comatula rosacea\ which 

 occurs not very rarely on 

 European coasts (Fig. 35). 

 This beautiful animal consists 

 of a central body or disk, 

 from which proceed five ra- 

 diating arms, which divide 

 almost directly after their 

 FIG. B&.iikisocrinus lofotmsis, a living origin into two secondary 



stalked Crinoid (after Wyville Thomson), K rn n O V,p>q on fhnf nltirrm+^lv 

 four times the natural size, a Stem ; b D es > sc imateiy 



Cup; cc Arms. there are produced ten long 



and slender rays. Each arm 



is furnished on both sides with a number of little jointed 

 lateral processes or " pinnae," so as to assume a feather-like 

 appearance, from which its popular name is derived. The 

 digestive system is furnished with both a mouth and a vent ; 



