BUFFALO SOCIETY OF NATURAL SCIENCES 33 



reaching the laboratory it was completely removed and 

 a cast taken of the impression in the rock. A photo- 

 graph of this specimen was compared with two subor- 

 bitals in the American Museum (Nos. 7298 and 7306 

 Newb. Coll.), which were figured by Newberry as of 

 Dinichthys terrelli.^ It agrees with these except that it 

 is even larger. 



Measurements cm. 



Total length (including process) 57.0 



Length of body of plate 41 .0' 



Greatest height of body of plate 27 .5 



Dinchthys intermedius ? Newberry 



E 2499 Impression of an antero-ventromedian (fig. 5), probably 

 referable to this species. 



Cleveland shale; Linndale, near Cleveland, Ohio, 

 Collected by W. L. Bryant, 1914. 



Median ventral plates of Dinichthys are rather rare. Of those 

 belonging to the Ohio species there are probably not more than a dozen 

 aU told in collections, notwithstanding that collecting has been going 

 on for nearly half a century. 



As seen from the figure, the present plate is bilaterally symmetrical, 

 tapers to a point, and was without question distinct from the postero- 

 ventromedian. It is known that in some species of Dinichthys, e.g., in 

 terrelli, the antero- and the postero-ventromedians were fused into a 

 single elongated plate, whereas in other species, for instance, in inter- 

 medius, the antero- and the postero-ventromedians were separate 

 plates, the antero-ventromedian narrowing posteriorly, and its extrem- 

 ity fitting into a socket on the outer face of the front end of the postero- 

 ventromedian. The present specimen clearly belongs to the type 

 which has the antero- and postero-ventromedians distinct; and from 

 its size it would appear to belong to Dinichthys intermedius. We have 

 compared it with three more or less perfect examples of this plate in 

 the American Museum collections. There is a good deal of variation 

 among these plates, and the present specimen differs somewhat from 

 all with which it has been compared, although in its general form and 

 proportions it agrees pretty well with one of these specimens, also 

 supposed to belong to Dinichthys intermedius. 



