MOEPHOLOGICAL PART. 47 



outlines are faintly indicated along the edges of the specimen. The middle 

 part of the truncated lower face is perfectly flat, and there are no traces 

 shown of an axial canal. But in an outward direction we find grouped 

 around a closed centre numerous small canals connecting with the interior. 

 These canals form upon the surface well defined ramifying grooves, which 

 pass out to the periphery, and seem to communicate with the surrounding 

 water. In another detached root, likewise with a flat bottom, the rami- 

 fications at the distal end were not exposed in the specimen, but were 

 opened out by grinding. The specimen has two root trunks of equal size^ 

 which are united at the bottom by an irregularly formed limestone deposit, 

 and around the projecting truncated lower end there are a number of 

 small openings, which connect with the canals from the two rootlets. 

 Whether the cirri of all Palgeozoic Crinoids open out at their ends, will 

 perhaps never be satisfactorily ascertained. We may state, however, that 

 the finest hair-like branches which have come under our observation are 

 perforated at their extremities. 



When in the Revision we directed attention to the variations in the size 

 and complexity of the axial canal (Part L, p. 15), we suggested that the 

 column was probably in some cases, and perhaps in all Palgeozoic Crinoids, 

 subservient to respiration. To this Dr. P. H. Carpenter* replied that he did 

 not think it unlikely that the pores near the base of the column may have 

 served to admit water into the stem, and thence into the coelom ; but he 

 doubted if the canals opened at the ends of the rootlets, concealed as 

 they were below the surface of the ooze, as the water introduced to the 

 stem by these passages could not have been very useful for respiratory 

 purposes. Neumayrf regarded the stem of the Crinoids a greatly modi- 

 fied organ, whose original form could only be explained by the structure of 

 certain Cystids ; and he thought it was primitively, as it is in that group, 

 a sac-like extension of the calyx, and was plated in a similar manner. In 

 corroboration of his views, he alludes to our observation that in Crinoids 

 with pentangular stems the faces and angles of the stem occupy a definite 

 position to the proximal ring of the plates in the calyx. 



Similar views were expressed by A. Agassiz. t He says : ^' That the pen- 

 tagonal stems hold a definite relation to the calyx has been clearly shown 



* Quart. Joura. of Geol. Soc, 1880, pp. 555-557. 



f Stamme des Thierreiches, p. 430. 



:|: Calamocrinus : Mem. Mus. Comp. Zool., Yol. XVII., p. 63. 



