80 PROCEEDINGS OP THE ACADEMY OP [188G. 



opinion are a kind of radicular cirrlii. In a specimen from tlie 

 Canada Survey Museum of Ottawa we found tlie lower face of 

 the stem covered by a calcareous deposit closing the canals. 

 This deposit appears to have been of a similar nature to that 

 which closes the centro-dorsal of Comatula and the nodal stem 

 joints of the Pentacrini, which, according to Wyville Thomson 

 and Carpenter (Chall. Rep., pp. 18, 19), occasionally break their 

 stems at a syz^'gy so as to become free. In the case of Ancyro- 

 crinus, however, the stem may have become detached and the 

 free state been the rule in the adult, as those stems with their 

 anchor attached are found in great abundance. 



The bottom plate in the calyx of the Gupressocrinidse and Gas- 

 terocomidas^ which we take to be a coalesced underbasal disk, has 

 been described heretofore as representing the upper joint of the 

 column, because the plate, at least in the adult, is undivided. 

 It is, however, well known that a fusion of one or more plates 

 takes place not only among basals, but also among unclerbasals ; 

 while, on the other hand, the columnar joints, which in most of 

 the Grinoidea are undivided, sometimes are tri- and quinque- 

 partite. The plate of Gupressocrinus unquestionably has the 

 position of the united underbasals ; it forms, like them, a part of 

 the calyx, as much so as the basals of Dolatocrinus and Stereo- 

 crinus, in which, as a general rule, the sutures are totally 

 obliterated, and in which the basal disk resembles most remark- 

 ably the underbasal disk in this family. It is to be regretted 

 that neither the central canal nor the angles of the column in 

 Gupressocrinus give any light on this question, the former being 

 circular, the column quadrangular ; but it seems to us that the 

 plate, if really representing a stem-joint, should be quadrangular, 

 in accordance with the other stem-joints in this genus, and not 

 pentangular, as we always find it. 



The muscle-plates of the Gupressoc7nnidee have a more hori- 

 zontal position than in the Symbathocrinidse^ and those of 

 different rays are laterally anchylosed, so as to form an annular 

 plate with a central opening. There is, besides, an interradial 

 lateral opening, and five pairs of radial ones. The central space 

 was probably covered by interradial and summit plates, but these 

 occupied a comparatively small space of the ventral surface, the 

 larger portion being covered by the muscle-plates. The inter- 

 radial opening represents the anus, the outer radial ones the 



