VERTEBRATES. 103 



This minute species is represented in the collection by a single, though per- 

 fect tooth. In its very small size and the oblique truncation of the narrower 

 end, it differs from the species that have been described, though similar to them 

 in general form. 



Figures 1 and 1 a represent the top and side views, natural size. 



Formation and locality: St. Louis limestone, Alton, Illinois. 



Sandalodus spatulatus, N. and "W. 



PI. X, Fig. 2. 



Teeth of medium size, broader extremity regularly rounded, 

 the other narrow, long-pointed, acute, slightly arched longitu- 

 dinally, strongly and regularly so transversely; enameled sur- 

 face coarsely and evenly punctate, and showing several curved 

 parallel furrows or lines of growth; length, 1 inch, 9 lines; 

 breadth, 7 lines; thickness, 3 lines. 



This species may be distinguished, at a glance, from its associates, by its size, 

 its coarsely punctate, rugose and furrowed surface, and by its having one end 

 broadly and evenly rounded, while the other is drawn out into a long, acute 

 point. 



Figure 1 is a view of the upper surface. 



Formation and locality: St. Louis limestone, Hardin county, Illinois. 



Sandalodus angustus, N. and W. 



PI. X, Pig. 3. 



Teeth small, very narrow, linear in outline, strongly arched 

 laterally, much more strongly so transversely; the crown sur- 

 face rising into a distinctly marked longitudinal ridge; surface 

 smooth, or roughened by the uniform and rather coarse punc- 

 tation. 



But a single specimen of this tooth is contained in the collection, and that 

 may prove to be but a fragment of a larger and differently formed one. 

 Figure 3 represents the upper surface, natural size. 

 Formation and locality: Keokuk limestone, Warsaw, Illinois. 



