68 NEW YORK STATE MUSEUM 



furnished a group of four teeth preserved in natural association. There is 

 but little difference in the form of upper and lower dental plates, and both 

 terminate anteriorly in prominent beaks. It is probable that the latter 

 character is a generic one, it having been observed in several other species 

 as well, but never in Ptyctodus. An excavation is noticed just back of the 

 beak in the upper dental plate where the terminal point of the lower came in 

 contact with it, thus proving that the relations between the two pairs were 

 the same as in Ptyctodus. The lower dental plate is deeper than the upper, 

 and marks of wear are frequently observed along the inner side of the func- 

 tional margin. 



Rhynchodus excavatus Newberry 



1877 Rhynchodus excavatus f . S. Newberry. Geol. Wis. 2: 397 



1878 Rhynchodus excavatus J.S.Newberry. N. Y. Acad. Sci. Ann. 1:192 

 1878 Rhynchodus occidentalis J. S. Neivberry. N. Y. Acad. Sci. Ann. 



1 : 192 

 1889 Rhynchodus excavatus J. S. Newberry. U. S. Geol. Sur. Monogr. 



16:50, pi. 29, fig. I 

 1898 Rhynchodus excavatus C. R. Eastman. Am. Nat. 32 : 486 

 1898 Rhynchodus occidentalis C. R. Eastman. Am. Nat. 32 : 485 



A comparison of the type specimen of the so called R. occi- 

 dentalis, which remains as yet unfigured, with an extensive series of 

 dental plates belonging to the earlier described R. excavatus, leads to 

 the conclusion that the two forms are identical. Indeed, it is certain that 

 Newberry would himself have recognized their identity, had he been 

 acquainted with more perfect specimens, such as are now accessible. Any 

 one may satisfy himself on this point who will take the trouble to verify 

 the original description of R. occidentalis, which reads as follows : 



Teeth of small size, much compressed. Anterior margin slightly 

 curved, but nearly vertical. Superior margin gently arched downward 

 from the prominent anterior point, forming a much compressed triturating 

 surface or edge. Posterior portion of upper margin acute edged. Exterior 

 lateral surface striated obliquely backward. Basal margin formed by the 

 edges of external and internal laminae, of which the edges are broken and 

 irregular. From the Hamilton limestone, Waverly, la. 



