128 NEW YORK STATE MUSEUM 



the functional margin denticulated. The observation is of sufficient weight, 

 in our opinion, to justify the transfer of this species from Coccosteus, where 

 it was doubtfully placed by Dr Clarke, to Dinichthys. Of special signifi- 

 cance from a systematic standpoint are the vomerine teeth, which are 

 described as follows by the same author : " Each is concave on the inner 

 surface, convex externally, and bore a somewhat extended apophysis, which 

 in each case has been broken off. There is no evidence of denticles or a 

 tuberculated surface ; the lower edge is, however, rather sharp and would 

 have served a cutting purpose." Amongst other minor peculiarities of 

 the head shield may be mentioned the subquadrate outline of the median 

 occipital, and the strong outward flexure of the preorbital sensory canals — 

 characters which one may regard as of specific importance. 



Associated with the head shield, and possibly belonging to the same 

 individual, certainly to the same species, is a specimen interpreted by Dr 

 Clarke with some reservation as a dorsomedian plate, and considered by 

 him to be divided by sutures into three parts. In the explanations of plates, 

 however, it is conceded that " the surface shows no satisfactory evidence of 

 sutures," and after a careful inspection of the original, the present writer is 

 convinced that the plate is normal in all respects, except that the external 

 surface has been somewhat injured. That others may judge of the char- 

 acters of this plate, an illustration is given of it in plate 2, figure 7. It 

 has a total length of 9 cm, and apparently did not exceed 2 mm in thick- 

 ness ; the carinal process has been broken away. The locality from which 

 both of these interesting specimens were obtained was the Livonia salt 

 shaft, in Livingston county. New York, at a depth of 828 feet below the 

 surface. They are preserved in the New York State Museum at Albany. 



Another interesting cranial fragment belonging to the same museum, 

 and from the same horizon as the preceding, is shown in plate 10, 

 figure I. In size, it indicates an individual about one third larger than the 

 type of D. h a 1 m o d e u s, and the tuberculation is relatively coarser, but 

 the form of the median occipital element agrees so closely with that of the 

 latter species, it is difficult to regard this as other than an adult example ; 



