AKT. 15 THE FOSSIL CRINOID GENUS VASOCRINUS KIRK 15 



several of the other specimens bore Lyon's label, it is probable that 

 tlie specimen was acquired with the Lyon collection. The close rela- 

 tionship of V. turhinatus to T^. valens makes it probable that it came 

 from the same horizon; that is, the JefFersonville limestone 

 (Ononcla<;a). 



Ha vino- reestablished the genus Vasocnnus on the foundation orig- 

 inally/ laid by Lyon, it remains to consider the status of Cyathocrinus 

 hexadactylus Lyon and Casseday. Wachsmuth and Springer ^ recog- 

 nized the identity of Hall's Cyathocrinus lyoni with Cyathocrlnus 

 hexadactylus Lyon and Casseday. They state " Lyon's name has 

 precedence, but being specifically as well as generically incorrect, we 

 adopt Professor Hall's later name." Their action, in those days of 

 loosely applied rules of nomenclature, is not more to be censured than 

 the rather naive mistake of Lyon and Casseday in taking the anal x 

 for a radial and the vertical median range of plates of the ventral 

 sac as an arm. Hence came the '' specifically incorrect " hexadactylus 

 Avhich we must adopt. Weller ^ has recognized the validity of Lyon 

 iind Casseday's name and places CyathocHnus lyoni Hall in proper 

 synonymy. This species, the structure of which has long been con- 

 sidered typical of VasocHmis, can not be placed in any described 

 genus. It is therefore made the type of a new genus, Pellecr'mus, and 

 a brief generic diagnosis is here given. 



PELLECRINUS, new genus 



Dorsal cup low, broad, composed of relatively thin plates. Radial 

 facet horseshoe-shaped, about one-half the width of the radial. Two 

 anal plates in the dorsal cup, rarely one : RA quadrangular, some- 

 times wanting; x heptagonal, approximately as large as the radials 

 and supporting three tube plates. Ventral sac stout, reaching about 

 one-half the height of the arms. Reaching to about one-half the 

 height of the ventral sac on the posterior side is a median line of 

 heavy plates. The remainder of this side is made up of fairly heavy 

 plates of smaller size. The sides and anterior portion of the sac is 

 composed of thinner plates, most of which show axial folds. The 

 anal opening lies at the apex of the ventral sac. The arms are long, 

 relatively slender, and bifurcate once. The third primibrach is the 

 axillary in all known species except one, when there are but two 

 primibrachs. On each ramus ramuli are borne on alternate sides. 

 In the known species the ramuli are borne by each second secundi- 

 brach. The ramuli themselves on the type species bear subramuli. 

 The stem is large, round in section, and composed of alternate wide 



* Wachsmntli, Charles, and Springer, Frank, Revision of the Palaeocrinoidea, pt. 1. p. 

 06 (321), 1S70. 



" Weller, Stuart, A bibliographic index of North American Carboniferous invertebrntos : 

 V. S. Geol. Survey Bull. 153, 1898. 



