FISHES OF THE CARBONIFEROUS SYSTEM. 157 
side they are more or less radiately striate and marked with the furrows of 
the nutrient vessels; the outside is granular like the exterior surfaces of 
most of the bones of Dinichthys. 
The dimensions of the cranium and appendages in this specimen of 
D. curtus are as follows: Length of cranium from occiput to nasal extremity 
ten inches; breadth between articulations with supra-scapulas, eight inches; 
breadth between posterior angles of the head, twelve inches; mandibles nine 
inches long by two and a half inches wide; suborbital plates seven inches 
long; posterior and flattened portion three and a half by four inches; 
supra-scapulas, relatively broader than any other species known, three and 
a half by six and a half inches in area. The mandibles have the general 
form of those of D. Terrelli and are much broader and more massive than 
those of D. Gouldiit. Back of the cutting edge the margin is set with two 
or three denticles of unequal size and just behind the anterior upturned 
point are éwo triangular prominences where most species of the genus have 
but a single one 
The figures on Pl. LIII represent a mandible, a supra-scapula, and a 
sclerotic plate, all of natural size. 
GLYPTASPIS, nov. gen. 
Placoderm fishes of large size belonging to the family Pterichthide. 
The body was protected by numerous thick, bony plates, of which those of 
the plastron were probably five in number, as in Pterichthys, Coccosteus, and 
Dinichthys. The middle one is lance-shaped or subrhomboidal, its central 
portion tuberculated, its margins sloped off and smoothed or striated by the 
overlap of the lateral ventral plates. The upper part of the body carried a 
number of lanceolate or ellipsoidal plates, of which the central parts are 
ornamented, the margins smooth and sloped down to thin edges. From the 
absence of marks of co-adaptation it seems probable that these plates did not 
overlap to form a carapace, but were set in the skin like the scutes of 
the sturgeons. The head plates and dentition are unknown. 
More material is wanted to give a satisfactory definition of the structure 
and relations of this genus, but the plates of the single species known are 
so striking in appearance, through their strong and characteristic ornamen- 
