122 



THE CRINOIDEA 



is further proved by the phylogeny of the Calceocrinidae. The 

 fact that x is wholly or partly in the cup, and t partly or wholly 

 outside, does not make them different morphological elements ; for 

 there is now admitted to be no difference between interambulacrals 

 and interbrachials, or between fixed and free brachials. Con- 

 sequently in this work the symbol x will always be applied to the 



Fio. XXIX. 



Upward iwssage of anal (x) in Ulowi niis. 1, anal area of " Ulocritnts" niairi; 2, posterior 

 view of U. Bnttxi; 3 and 4, U. Kansasensis, the cup from posterior and from above, x $ 

 (From Bather, after Miller & Gurley.) 



proximal plate of the median line of the anal tube, whatever its 

 position. 



Modification of the cup is not confined to the fixed brachials 

 and interbrachials, but also affects the patina. We have discussed 

 the disappearance of IBB. We have also to note a tendency to 

 fusion in the plates of the proximal circlet, whether IBB or BB, 

 and their change of shape due to the introduction of anals into the 



3 4 



Fio. XXX. 



(After W. B. Carpenter and M. Sure.) Originating 

 . -",--- " > two small 



fragments remain at the base of the anal tube (t). The dotted 

 gut. These figures also show change in shape of RR, and atrophy of orals (0). 



Migration of the anal in Antedon. 



between RR, the plate x gradually moves upwards^eventually atrophying till only two small 



ed lines in 1 show the course of the 



patina. The first stage is the fusion of one pair, producing 1 

 large and 3 small plates (Fig. XXXI. 2). This is almost entirely 

 restricted to monocyclic genera, where the plates that fuse are the 

 right and left anterior basals. Next comes the fusion of two pair, 

 producing 1 small and 2 large plates (Fig. XXXI. 3). This occurs 

 in both Mono- and Di-cyclica. In the former the small plate is 

 the left anterior basal, or rarely left posterior basal ; whereas 

 in Eublastoidea it is the right anterior basal (Fig. XXXI. 4). 

 In Dicyclica three infrabasals have been observed only among 



