

106 PALAEONTOLOGY OF ILLINOIS. 



Genus RINODUS, N. and W. 



Gen. Char. — Teeth of medium or large size, elongated in 

 form, with an expanded, sub-conical base, and a flattened or 

 furrowed crown; enamel tubes arranged in transverse rows, 

 producing on the triturating surface a series of transverse fur- 

 rows and ridges which give, it a file-like roughness. 



In form and microscopic structure these teeth depart so widely from all 

 known living or fossil types that at present we are scarely able to offer even a 

 conjecture in reference to their affinities. They would seem to have been 

 formed rather for grinding than crushing, and in the alternation of bands of 

 harder and softer material in the enameled coating of the crown, we have the 

 adaptation of means to an end, as clearly shown as in the grinders of the 

 Elephant, which indeed seem to be foreshadowed in this the dentition of a 

 Devonian fish. 



Rinodus calceolus, N. and W. 



PI. X, Figs. 10, 10a, 10 b, 10 c. 



Teeth laterally compressed, forming an unequal and irregu- 

 lar frustrum of a cone; the summit truncated, compressed and 

 deeply furrowed longitudinally ; base more or less excavated 

 beneath. The general form is very much that of a low shoe, 

 a resemblance which has suggested the specific name given to 

 it. The sides of the tooth are marked with a series of more 

 or less interrupted and inosculating, horizontal, raised lines and 

 furrows, of nearly equal breadth. The summit is occupied by 

 a plate of dense enamel marked like the sides, but across this 

 the lines run transversely, giving it a file-like surface. In the 

 specimens before us this enameled crown is hollowed into a 

 broad, longitudinal sulcus ; when examined under a powerful 

 glass, the roughening of the triturating surface is seen to be 

 affected by the arrangement of the enameled tubes, which are 

 placed in rows side by side, forming sulci which are separated 

 by ridges of harder material. The base is deeply excavated 



