1888.] NATURAL SCIENCES OF PHILADELPHIA. 359 



The two groups would be separated chiefly upon the condition of the 

 mouth, and the name "Stomatocrinoidea," which we proposed in 

 1879 (Revision I, p. 22), might be revived. The greatest objection 

 to this plan, however, lies in the possibility, as before mentioned, of 

 finding an Ichthyocrinoid with closed mouth, or a Haplocrinoid 

 with parted orals, wdiich w^ould upset the whole arrangement. 



To attempt to modify the definition of the Palaeocriuoidea so as 

 to admit forms with an external mouth, is in our opinion entirely 

 out of the question, and would simply increase the difiiculties now 

 encountered, because there could not be pointed out a single reliable 

 character by which the two groups could be distinguished. 



After considering the question in all its new aspects, as presented 

 by the facts recently brought to light, it is our best judgment, that 

 all attempts to subdivide the Crinoidea by separating the palaeozoic 

 from the mesozoic and later forms as natural divisions, will have to 

 be abandoned, and some mode of separation sought for, entirely in- 

 dependent of geological age. In that case, the names Palaeocrinoidea 

 and Neocrinoidea — unless in the sense of mere conventional terras 

 for designating the palaeozoic and later crinoids — will have to be 

 laid aside. 



To this end we think that four w^ell defined groups can be dis- 

 tinguished as independent primary divisions of the Crinoidea, viz : 



1. Camarata. 



2. Inadunata, including the branches Larviformia and Fistulata. 



3. Articulata, ^ including the Ichthyocrinidae, and possibly Uin- 

 tacrinus and Thaumatocrimis. 



4. A fourth division to include the most of the mesozoic and re- 

 cent crinoids, for which the name Canaliculata^ might be xevy ap- 

 propriately adopted. These divisions will be subordei'S or orders, 

 depending upon the rank which may be ultimately assigned to the 

 Crinoidea — a question we think still open for discussion. In the 

 definition of them many classificatory criteria, such as the condition 

 of the mouth, the presence or absence of interradials, the relative 

 proportions of the actinal and abactinal regions in the calyx, which 



^ The Crotalociinidae, which we formerly assigned to the Articulata, have 

 been found to i^elong to the Camarata, as we have shown at length in another 

 paper. 



2 This name was proposed by frof. E. J. Chapman in a paper entitled -'A 

 classification of Crinoids," Toronto, 1874, to include the genera Penlacrinus, 

 Antedon, Encrinus, Eugenia crinns, Apiocrinus, Botirgiieticrinus, and Rhizo- 

 crinus. 



