360 PROCEEDINGS OF THE ACADEMY OF [1888. 



when applied to the okler and later crinoids seem to lose much of 

 their significance, will form strong and distinctive characters. Pa- 

 laeozoic and recent crinoids may, if necessary, be brought together in 

 the same group, according to their zoological characters, free from 

 embarrassment arising from restrictions as to geological age. 



The Camarata, Inadunata and Articulata would be defined, as to 

 their most general characteristics, substantially as we have already 

 defined them in the Revision of the Palaeocrinoidea, with some 

 modifications as to the ventral structure in the Inadunata and Ar- 

 ticulata, to conform to recent discoveries. 



We are strongly of the opinion that the recent genera Holopus, 

 Batliycrinus and Hyocrlnus might very properly be arranged under 

 the Larviformia. All three are monocyclic, and like the Haplo- 

 crinidae and Symbathocrinidae retain through life large oral plates. 

 But while the orals in these two fimilies are closed and rest direct- 

 ly upon the radials, in the above named recent forms they are part- 

 ed, and separated from the radials by a narrow band of perisome, 

 which, we strongly suspect, was also the case in the Gasterocomidae. 

 The aberrant genus Thmimatocrinus might be referred to the Ar- 

 ticulata, with which, for the most part, it agrees in the asymmetry 

 of the calyx and the construction of the azygous side. Uintacrinns 

 will very likel}- fill into the same group ; while the Encrinidae will 

 jDrobably find a resting place among the Fistulata, and perhaps also 

 3Ia7'supites. 



The removal of these genera would leave the Canaliculata as a 

 very compact, well defined group. It would contain only crinoids 

 "which are dicyclic, or built upon the dicyclic plan, and in which the 

 underl)asals are anchylosed to the top-stem-joint, the two together 

 forming the centro-dorsal. All of them would be free from any 

 disturbance by anal plates, and the basals in all of them, so far as 

 known, would be perforated by interradial canals or furrows in con- 

 nection with the chambered organ. 



The disposition of the later crinoids, as herein indicated, is mere- 

 ly suggestive, as we prefer to leave their arrangement to Dr. P. H. 

 Carpenter, who has made them a special study. 



We shall not at present undertake more than to submit for the 

 consideration of our fellow naturalists the conclusions to which we 

 have been led by the evidence of recent discoveries, leaving to a 

 future occasion the framing of detailed definitions of the divisions 

 we have proposed in case they should meet with favor, A con- 



