NO. 3 ON THE FOSSIL CRINOID FAMILY CATILLOCRINIDAE I9 



ment of radials and arms, already mentioned, passed into an im- 

 poverished condition with which the line was extinguished. 



Such a change in the anal structure as above described would in 

 other groups be considered as ground for generic separation, but in 

 a type so highly specialized as this, on the eve of its extinction, these 

 characters are so completely overbalanced by those which have become 

 dominant, that they may well be regarded as of secondary importance. 

 The raised process is present in the Devonian genus, but apparently 

 not in the Timor form ; this would indicate that the tube structure in 

 Mycocrinus was according to the plan of C. tennesseeae and its allies, 

 while that of P aracatillocrinus was like that of C. bradleyi and C. 

 carpenteri. 



If it should be thought that my view of the significance of this 

 character is too conservative, then the later section might be ranked 

 as a new genus under the name Eiuatillocrinus, with E. bradleyi as 

 genotype. But in order to be consistent this should be followed up 

 by setting ofif C. carpenteri as another genus on account of its dif- 

 ference in radials and arms. 



With the enormous space enclosed by the tube in proportion to 

 the small size of the cup, it must have had some other function than 

 that of a mere excretory organ. It may have lodged the genital 

 apparatus. 



RELATIONS WITH OTHER GENERA 



As already remarked, the tube is of the same type that occurs in 

 Pisocrinus, Deltacrinus and Synbathocriims, and doubtless through- 

 out the families to which they belong. As it is rarely seen in these 

 genera, I am giving figures of some specimens in which it is exposed 

 (pi. 5, figs, ij 3, 9, 20, 21). They show a certain relationship among 

 these forms, notwithstanding their remarkable dififerences and spe- 

 cializations in other characters. Indeed the similarity is somewhat 

 striking between Synbathocrinus and Catillocrinus, the one a model 

 of symmetric adjustment of all its parts, and the other an example 

 of the extreme to which a disturbance of the most stable element in 

 crinoid morphology can go. 



Aside from the asymmetry of the radials, the dififerences between 

 the two genera are chiefly matters of degree. The general form of 

 cup, plan of construction of tube and arms, and the mutual relation of 

 these parts, are substantially the same in both, only the relative pro- 

 portions are reversed. With the five strong arms in SynbatJwcrinus 

 the tube which they enclose is dwarf-ed, while in Catillocrinus it is 



