290 Messrs. P. H. Carpenter and R. Etlieridge, Jun., 



species not being so clear as could be desired, Major Austin, 

 F.G.S., was communicated with for further details of P. 

 isacohus than are contained in the description given by him- 

 self and his son. Major Austin very kindly replied that his 

 specimens had unfortunately been mislaid. We are therefore 

 unable to institute a close and detailed comparison between 

 P. isacohus and our Allagecrinus. We propose to call the 

 latter^. Austinii, Ether. & Carp., as a slight tribute of respect 

 to Major Austin in connexion with his work on the Carbo- 

 niferous Crinoidea. 



According to Messrs. Austin, " the dorso-central and periso- 

 mic plates (of P. isacohus) appear to agree in number with the 

 typical species " of Poteriocrinus. H this be the case, P. 

 isacohus is not in the least related to Allagecrinus. But in the 

 figure of it given by the Messrs. Austin there is no indica- 

 tion whatever of the presence of two rows of plates below the 

 radials*. We believe the plates which are represented as 

 forming the greater part of the calyx to be the radials, and 

 the ring upon which they rest to consist of five closely united 

 basals, as in our specimens. Above these radials the Messrs. 

 Austin's figure is incomplete : but one portion of it appears to 

 represent the end of a short first brachial which has been dis- 

 placed 5 and upon this there seems to have been an elongated 

 axillary brachial, each face of which bore a similarly elon- 

 gated axillary that supported two arms. Hence there were 

 probably twenty arms. 



Mr. Percy Sladen has proposed to establish a new genus, 

 Dactylocrinus'\^ for the fossils described by Miller and the 

 Messrs. Austin respectively under the name Poteriocrinus 

 tenuis. He takes that figured by Messrs. Austin as the type 

 of his new genus, and calls it B. loreus ; while the Poterio- 

 crinus tenuis, Miller, becomes the Dactylocrinus tenuis of 

 Sladen, who thus continues : — '' The P. isacohus of Messrs. 

 Austin seems identical with the present species. In any case 

 it is very much nearer than the fossil figured by them as P. 

 tenuis.^'' We regret that we are unable to accept this view of 



* The " first series of perisomic plates" of Messrs. Austin are those 

 which one of us has proposed to call " under-basals." This name has 

 been adopted by Messrs. Wachsniuth and Springer and by Prof. Zittel. 

 The " second series of perisomic plates " are the " parabasals " or " sub- 

 radials " of the old nomenclature, and the " basals " of the more rational 

 modern one. The dorso-central plate described in Poteriocrinus by 

 Messrs. Austin is not recognized by other authors as occurring in this 

 genus at all. 



t " On the genus Poteriocrinus and Allied Forms," Proceedings of the 

 Geological and I'olytechnic Society of the West Ridiug of Yorkshire, 

 1877, pp. 245-247. 



