ADDITIONS AND COREECTIONS. 355 



or three forms, presents the gradation of types from the corals of the family Cyatho- 

 phyllidese to the bryozoid forms. 



NOTE C. 



CRINOIDEiE. 



Thysanocrinus. It maybe uncertain whether the portions of crinoids referred to this 

 genus on Plate xlii, figs. 2, 3 & 4, really belong to it, or to some other genus. An op- 

 portunity of examining some other specimens has suggested a doubt as to the propriety 

 of this reference. 



In the genera Glyptaster and Lyriocrinus, I have detected the existence of tentacula 

 attached to tlie plates of the arms. The same character probably exists in Dendrocrinus 

 and Macrostylocrinus ; but up to this time, I have failed to discover it in Ichthyocrinus 

 and Lecanoceinus. I have likewise ascertained the existence of tentacula in the Stepnano- 

 cRiNus, as shown on Plate xlviii. Since these appendages exist also in the cystideans, we 

 may infer that they form a part of the organization in all Crinoideje. 



Genus Hemicystites, page 69. This genus is apparently identical with Agelacrinites 

 of Vantjxem, the description and figure of which I had overlooked at the time this vo- 

 lume was written. This name was given by Mr. Vanuxem to a fossil of the Hamilton 

 group, to indicate the occurrence of several in connexion or proximity to each other ; a 

 circumstance, however, which will not be found constant, or of generic importance 



[ Paljeoktology — Vol. u.] 46 



