INVERTEBRATE PALAEONTOLOGY. 265 



but. sometimes curved or variously bent, and often closely crowded. They 

 are faintly marked, at regular intervals, by obscure annular impressions, 

 which pass around somewhat obliquely ; and some of them are at places 

 provided with a few transverse septa. Diameter varying from 0.20 to 0.35 

 inch. 



This species will be distinguished from the preceding by the absence 

 of a notch or sinus in the bonier of its posterior side, and by having its dorsal 

 margin rounding regularly down behind, instead of nearly horizontal. It also 

 differs in having no traces of the obscure, oblique, posterior sulcus on internal 

 casts, and in the annular, or ringed, appearance of its tubes, which are also 

 larger than those of that species. 



Locality and position, — Same as last. 

 34 H 



