382 Mr. F. A. Bather on British Fossil Grinoids. 



acknowledged, that I have not judged it necessary to enter 

 into details. But there is one point in which I differ very 

 materially from previous writers ; that is the separation of 

 these forms which I have just described as descended from 

 Botryocrinus. Other authors place them close beside Pot- 

 eriocrinus (s. str.) and Scaphiocrinus. But the dichotoraous 

 many-branched arms of these two genera and their allies 

 could hardly have sprung from the bifurcate, heavily pinnu- 

 late arms of Decadocrinus, Graphtocrinus, and 8cytalecrinus } 

 without leaving some traces of the process ; these latter closely 

 resemble the arms of Vasocrinus and of some species of 

 Botryocrinus. This seems a sufficient reason for separating 

 the two groups ; I have already alluded to differences of 

 articulation connected therewith ; besides this there is a 

 general similarity of what is called " habit " in the members 

 of each group, and there is certainly nothing to oppose their 

 alliance in this manner. 



To return to the Cyathocrinus group ; that genus itself 

 persists unchanged to the Coal-measures. In Codiacrinus 

 the brachianal seems to have been again raised above the 

 level of the raclials, and has not yet been observed. Achrad- 

 ocrinus shows an atrophy of the brachianal, and a diminu- 

 tion of the arms, characters which are still more pronounced 

 in Hypocrinus. Lecythocrinus is probably a descendant of 

 Gissocrinus } and Lecythiocrinus of Codiacrinus. 



The Dorsal Cup of Belemnocrinus, except for its mono- 

 cyclic base, resembles that of Cyathocrinus • the arms show 

 a tendency to the development of armlets, but are not a great 

 advance on those of Cyathocrinus : on the whole I incline to 

 the belief that this genus is descended from Cyathocrinus, 

 but that intermediate stages have not yet been found. IIolo- 

 crinus is an advance on Belemnocrinus both as regards atrophy 

 of the brachianal and the conversion of armlets into stout 

 pinnules. 



In each of these lines there is a gradual development of 

 articulation ; this, however, can merely serve to confirm the 

 general evolution, and it varies so much according to the needs 

 of individual genera that under no circumstances could any 

 great argument be based on it. 



Classification. 



The Genealogy of the Fistulata may be summed up in the 

 accompanying table (Table II.). It is of course needless in 

 the present year of grace to point out the differences between 

 a scheme such as this, which shows general relationships, and 



