V. Botryocrinus. 411 



— there is a mistake somewhere in Wachsmuth and Springer's 

 description, although this is a point on which they lay stress 

 — in Botryocrinus, however, the number varies from 1 to 6. 

 Here too then it is hard to see how any great distinction can 

 be drawn ; and the number of costals is rarely a point of 

 much importance, even as a specific character, in the older 

 Crinoids. 



The Ventral Sac of Barycrinus is unknown, or was so in 

 1879 ; that of Vasocrinus is said to have a " series of large 

 quadrangular plates at the base, the lower ones as wide, but 

 much higher than the radials." It is very easy to see how 

 this structure may have arisen, for, as previously stated, the 

 median posterior region of the sac in Botryocrinus is usually 

 more solid than the rest, and in B. ramosus the proximal 

 median plate is just such a one as in Vasocrinus. Certainly 

 this difference appears no greater than that which obtaitis in 

 the various species of Botryocrinus. In both Vasocrinus and 

 Barycrinus the radian al is occasionally absent ; but as in ail 

 species where it occurs it is very small, and as the species in 

 which it is absent have not hitherto been placed in separate 

 genera, this fact can hardly affect the separation of the genera 

 themselves. 



The Stem in Barycrinus is subpentagonal, in Vasocrinus it 

 is round, in Botryocrinus it is either. In Barycrinus radial 

 sutures are well marked, in Vasocrinus they have only been 

 seen in V. dilatatus. in Botryocrinus they vary in the extent 

 to which they are visible. The lumen in Barycrinus is large 

 and " highly organized," though in what the organization 

 consists is doubtful; in Vasocrinus it is " comparatively small 

 and simply constructed," in Botryocrinus it is small and 

 pentagonal. 



Now it must be confessed that these differences are of no 

 great importance, and that some difficulty is experienced in 

 drawing up a diagnosis of Botryocrinus that shall adequately 

 distinguish it from the two other genera. Since, however, I 

 have not had access to many specimens of either Vasocrinus 

 or Barycrinus, I have thought it better simply to describe the 

 long-known genus Botryocrinus as fully as possible, with the 

 aid of new material, and to leave to the American palaeon- 

 tologists the task of comparing it afresh with these other more 

 particularly American genera. The date of Vasocrinus is 

 1857, of Barycrinus 1S68 ; Botryocrinus is ten years younger, 

 and, should it prove identical with either of these, must yield 

 its name. I commit it therefore to the tenderest mercies of 

 my fellow- workers beyond the Ocean. 



