22 2 AYERS AND JACKSON. [Vol. XVII. 



teeth, for Girard counted in his type specimens with 14 gills 

 if I if' while Putnam found l| 1 1| or W \ if in the material he 

 studied from Talcahuano Bay (Hassler expedition), reported as 

 having 10 gills. 



Lacepede's example from Chili had the very unusual dental 

 formula of -Y- 1 Y-. 



A critical histological study of the dental structures of 

 Bdellostoma is reserved for a separate paper. But it may be 

 mentioned that the hollow bases of the corneous teeth rest 

 upon soft dental papillae, which are fused together below into 

 a bar extending the entire length of the row of teeth. These 

 papillae are epidermal in origin, and the teeth are simply corni- 

 fied sheaths of the epidermal elevations upon the dental plate. 

 They are easily sectioned when imbedded in celloidin, and 

 show no traces of dentine, enamel, bone, or calcareous matter 

 of any kind. 



March, 1S98. 



(To be contiuued.) 



