48 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



note that some of the cirri in the distal portion of the column are 

 longer than the remainder, indicating that they were specially modi- 

 fied as grasping organs. The comparatively minute size of the crown 

 and the extraordinary development of cirri suggest that the activity 

 of the latter organs may have been of no small service in the propul- 

 sion of the animal. Bather (1893) has suggested that the alternate 

 spring-like action of coiling and uncoiling on the part of the stem 

 may have brought about movement. 



BracJiiocrinus . — BracJiiocrinus, of which probably only portions of 

 the column are known, undoubtedly was not permanently affixed. 

 I have examined the distal portions of several BracMocrinus columns 

 and in each instance have found the same fused into a small knob 

 (PI. 5, fig. 8) and showing no signs of cementation. 



BracJiiocrinus is structurally similar to Heri^etocrinus in that the 

 column bears two rows of cirri. These are much heavier than in 

 the case of Herpetocrinus and are composed of bead-like ossicles. The 

 column is round, and it does not seem wholly certain that any but the 

 distal portion bears lateral appendages. In one or two instances 

 the portion of the column preserved appears involute. This coiling 

 suggests, however, that the distal portion of the column forms the 

 center of the coil, and not the proximal end, with the attached crown. 

 If such be the case, we must consider BracMocrinus as having the 

 distal portion of the column flexible, more or less prehensile, and 

 occasionally involute. For a short distance up the column is a 

 double row of cirri, by means of which objects could be grasped. So 

 considered BracMocrinus is not closely comparable to Herpetocrinus, 

 as has hitherto been thought. 



MiUericrinus prattii. — In the case of Millericrinus prattii, from the 

 Jurassic, we have one of the most remarkable manifestations of an 

 eleutherozoic habit to be noted among the stalked Pelmatozoa. 

 Indeed, according to the classification here employed, it is a matter 

 of no little uncertainty as whether to place Millericrinus prattii in 

 this or the succeeding group. Dependent upon the variable degree 

 of specialization shown by certain individuals, the species might 

 indifferently be placed in either division. In all the preceding types 

 we may note that the column is persistently present. It is moreover 

 functional to a certain degree, acting as a ballast, drag, or organ of 

 attachment for the organism. In this species, however, there is a 

 strong tendency toward the complete elimination of the column. 

 This form has been excellently figured and described by Carpenter 

 (1882). Several of his figures are reproduced here on Plate 6. The 

 characters shown by this species are apparently distinctive and not 

 common to any other member of the genus. 



The column is round and tapers quite rapidly distad. The longest 

 stem noted is a trifle more than 50 mm, in length in the case of the 



