264 



teeth, ends in a triangular process vvitli a lozeuge-like articular surface Ibr 

 symphysial attachment with the bone of the opposite side. 

 Measurements derived from seven specimens are as follows: 



Estim.ated. 



Family Raice. 



ONCOBATIS. 



Oncobatis pentagonus. 



An extinct ray, before alluded to, is indicated by a single dermal Ijone, of 

 which two views are given, of the natural size, in Figs. 18, 19, Plate XVII. 

 The bone has a pentagonal outline with curved margins, with the under or 

 inner surface strongly convex and smooth. The upper or free surface presents 

 five sloping planes more or less well defined by prominent borders. Less 

 lliaii half the extent of the external surface at the center is occupied by an 

 areola of thin enameloid substance which is smooth and shining nnd marked 

 with concentric lines. The summit of the lione, in the center of the areola, 

 l)rojects as a point of harder and more translucent osseous substance. 



