.332 PROCEEDINGS OF THE ACADEMY OP [1879. 



same difficulty exists in regard to Austin's figures, who has repre- 

 sented under P. crassus two or more distinct species. 



The identification of P. tenuis, Miller's second species, is equally 

 doubtful, and in our opinion altogether unreliable. The arms as 

 there figured certainly do not belong to that calyx nor that column, 

 and we are confident that the two latter pertain to Poteriocrinus 

 and the former to Cyathocrinus. We may here remark that while 

 we have experienced scarcel} 7 any difficulty in referring the known 

 species to Poteriocrinus and Cyathocrinus respectively, we find 

 in all of Miller's species, in one way or another, characters alto- 

 gether at variance with the rules we have laid down for distinguish- 

 ing the two genera. Under these circumstances the question arises 

 whether it is not in the interest of science to adopt a new or at 

 least an additional type for the genus. This may somewhat con- 

 flict with the rules and practices of naturalists, but in this case we 

 consider it the only adequate remedy. We accordingly propose 

 for this purpose Poteriocrinus notabilis Meek & Worthen, from 

 the Burlington limestone, the original of which, formerly in the 

 collection of C. W. and now in the Museum of Comp. Zool. of 

 Cambridge, Mass., is figured in the Geol. Rep. 111., vol. v., pi. 1, 

 fig. 9. We have selected this species because it is found in very 

 perfect preservation, and because it agrees most closely with Mil- 

 ler's typical species, and certainly belongs to the same division. 



Making this the typical form, we further propose as sections 

 under it Scaphiocrinus Hall, with S. dichotomies Hall's second 

 species (the first being referred to Graphiocrinus) for type; 

 Parisocrinus W. & Spr., with Poteriocr. perplexus M. & W.; 

 Pachylocrinus W. & Spr., with Poteriocr. subsequalis W. & Spr. 

 (Hall's Poteriocr. sequalis)', Scylalocrinus W. & Spr., with Poteri- 

 ocr. robustus Hall, Decadocrinus, with Scaphiocr. scalaris M. & 

 W., respectively as types; and as we regard these sections rather 

 as variations of the genus, which hardly rise to the dignity of 

 subgenera, we shall for the present write the names with that of 

 the parent genus prefixed. There are some other species, only 

 knowm from the calyx which could not be satisfactorily arranged 

 under the above groups, and these will be found in a list by them- 

 selves. 



Generic Diagnosis. General form of body with arms, elongate, 

 subcylindrical, expanding uniformly upward. Calyx very variable 



