280 



CEINOIDEA. 



pears on the lower and lateral aspects of the cup. Two 

 other rows of radials succeed these, the tertiary radials being 

 unusually large, and each supporting the bases of two arms. 

 The inter-radial plates are developed in a most singular 

 manner, so as to form a series of five linear, clavate pro- 

 cesses, which Separate and support the arms ; five other 

 precisely similar processes being borne by the axillary 

 radials. The arms thus come to lie in deep grooves or 

 niches in the sides of the calice, the upper surface of which 

 they do not reach. The upper surface is completely vaulted 

 over, and is mainly formed by the upper ends of the ten 

 inter-brachial processes just spoken of, in the centre of which 

 is a small circular (oral ?) aperture, surrounded by four 

 plates. Without entering further into the structure of this 

 genus, it is clear that it presents us with an entirely unique 

 type, in which the mode of existence must have been very 

 unlike that of the ordinary Crinoids. This is shown by the 

 fact that the arms are shorter than the 

 calyx, lying freely in grooves in its 

 sides. Billings has shown that the 

 brachial grooves in Eucalyptocrinus per- 

 forate the walls of the calyx at the 

 bases of the arms, and thus gain the 

 interior of the cup (Geol. Survey of 

 Canada, Decade III. p. 24). It may 

 therefore be suggested, with some pro- 

 bability, that the animal obtained its 

 food by means of currents set up in 

 the surrounding water by the cilia lining 

 the brachial grooves (as in the ordinary 

 Crinoids), but that the real oral aper- 

 ture was placed at some unknown point, 

 deep within the cup, and that the open- 



j nJ ftt tf ie top Q f t j ie ca l yx usually SUp- 



J J L 



posed to be the mouth, is really the 



anus. 



The family of the Glyptocrinidce, represented by the Silurian 

 G-lyptocrinuSj agrees with the preceding families in having 110 

 parabasals, but there are five basals, succeeded by three rows 



Fig. 167. Side view of the 

 cup ofCiipressoerinus cross-Ms, 

 with the arms folded up, of 

 the natural size. Devonian. 

 (After Schultze.) 



