FISHES OF THE CARBONIFEROUS SYSTEM. 151 
height, smooth, and relatively thin; suborbital bone six and a half inches 
long, broadly rounded behind, with a deep sinus above to receive the eye; 
it is relatively thin, and was apparently covered by integument; eye very 
large, orbit elliptical, one and a half by one and a quarter inches in diameter, 
surrounded by four thin, anchylosed, sclerotic plates, which are on the out- 
side smooth or finely granulated, within radiately striate. 
This species was discovered by Dr. D. T. Gould in 1886 in the valley 
of Rocky River, below Berea, Ohio. The head, dorsomedian and supra- 
scapular plates, a suborbital bone, one premaxillary, and portions of two 
mandibles were found together, and with them two circles of sclerotic plates, 
one dislocated the other entire, by which the orbits were surrounded. 
These circles were formed of four pieces nearly equal in size; the aperture 
of the eye was elliptical, an inch and a half long; the ring of cireumorbital 
plates was somewhat elliptical in outline and four inches in its longest 
diameter. In life the eye must have had somewhat the aspect of that of 
Ichthyosaurus and was relatively as large. Whether other species of Dinich- 
thys had eyes of similar construction and equal size can not yet be said, but 
the form and size of the suborbital plates and the depth of the sinus which 
received the ocular apparatus indicate large eyes in all the genus, but rela- 
tively smaller than in the present species. To maintain the same propor- 
tious the eyes of D. Terrelli would need to be about a foot in diameter. It 
seems probable, too, that D. Gouldii was peculiar in having ossified plates 
around the eye orbit. If the larger species of the genus had possessed sim- 
ilar bony plates we ought long since to have become familiar with them, but 
none have been found; and we may hence infer that the external envelopes 
of the eye were cartilaginous. This species has been dedicated to Dr. D.'T. 
Gould, the discoverer. 
DINICHTHYS CORRUGATUS, 0. sp. 
Plate VI, Figs. 3, 3°. 
Of this species we have only the anterior half of a mandible. This 
mandible was originally six inches long but all the flattened spatulate por- 
tion is wanting. That part which has been preserved is the thicker, denser, 
and more exposed anterior end. This is broken along the upper margin, so 
