1 



234 The Ottawa Naturalist. [March 



over the summit of the second joint; this must be erroneous 

 if the species are identicaL Mouth. ^The ambulacra meet 

 at or near the centre of the disc and do not enter the calyx 

 at the edge of the radials as stated by Wachsmuth and Springer. 

 A central oral aperture must exist but it is not observable, 

 being rigidly closed in by the tight fitting and interlocking 

 ambulacral cover-plates. Carpenter's figures of the oral aspect 

 are extremely variable and confusing; it is difficult to co- 

 relate his diagrams. Anus. Despite Wachsmuth and Springer's 

 obiection, Wetherby's statement as to the existence of a 

 valvular pyramid is correct. That this pyramid is surrounded 

 by a series of small plates is here recorded for the first time. 

 This feature tends to increase the resemblance of the present 

 genus to H ybocrinus , for the same structure was observed by 

 W. R. Billings in the latter genus and is figured for Carabo- 

 crinus by Wachsmuth and Springer.* 



Locality. ^Mercer Covmty, Kentucky; Trent Valley Canal, 

 Eldon tp., Victoria County, Ont., two miles from Kirkfield, 

 J. Townsend, collector. No. 567 T. University of Toronto 

 Musetxm. 



Hybocystis eldonensis, sp. nov. 



(Plate II., Fig. 4) 



This species is founded on one well preserved, specimen 

 although two others are at hand. The latter, however, are 

 somewhat larger and stouter, so that, in order to avoid any 

 specific confusion, the description is confined to the single 

 specimen. The present species is much smaller than H. prob- 

 lematicus, being only about seven millimetres in vertical extent. 

 It shows the same asymetric shape, the column being excentric 

 and the vault much elevated on the anal side. The calycine 

 plates are quite similar but the upper azygous plate is relatively 

 smaller; its presence, indeed, is more to be inferred than ob- 

 served. The ventral sac and anus are likewise similar, the 

 circlet of small plates and the dome-like valvular pyramid 

 being clearly shown. The ambulacral tracts on the tegmen 

 are well closed by rigid cover-pieces which are relatively larger 

 than in the genotype. The most pronounced difference is in 

 the fact that the two calycine ambulacra do not extend over 

 the basals but are confined to the radials, where they are 

 bolstered up on relatively larger tumid pads. The cover- 

 plates are large and distinct with the individual ossicles of the 

 two rows alternating. There is no trace of an ambulacral 



* North American Crinoidea Camerata, p. 137. 



