FISHES OF THE CARBONIFEROUS SYSTEM. 147 
about in the vicinity. None of these heads showed any traces of the eye 
orbits, and they remained unknown until 1885, when Drs. Gould and 
Clark, of Berea, Ohio, found in the valley of Rocky River the head of a 
small and new species of Dinichthys (D. Gouldii, N.), of which the eye orbits 
were preserved. The length of the cranium was about a foot; the opening 
of the eye was elliptical in outline, an inch by an inch and a quarter in 
diameter, and was surrounded by a circle four inches in diameter, composed 
of four sclerotic plates. This showed that the eye of Dinéchthys Gouldit was 
much like that of Ichthyosaurus and relatively as large. 
In regard to the structure of the external eye in the other species of 
Dinichthys we have until recently had no information. It was deemed 
probable that their eyes were provided with sclerotic plates, but from the 
fact that they had not been found with the other portions of the head I had 
supposed that they were cartilaginous and had perished. Since the MS. 
for this monograph was sent to the printers a head of Dinichthys curtus has 
been found by Professor Kepler at Linndale, Ohio, which shows that the 
eyes of this species also were protected by bony sclerotic plates. They are 
described on another page. 
Several years ago Mr. Terrell called my attention to some perforated 
bones which he found adhering to the inside of the skull of Dinichthys Ter- 
relli. They were not always in the same position, but they were two in 
number, one on each side, and located well within and near the anterior 
extremity of the head. ‘These bones were conical in form and elliptical in 
‘ section, having a broad excavated cup at the larger end, a narrow and 
deeper one at the smaller, with an orifice a quarter of an inch in diameter 
connecting the two depressions. The shallower cup of the larger end was 
uniformly arched and had a kind of raphe on the bottom along the line of 
greatest diameter. From this radiated a series of dark bands, bundles of 
tubes or fibers, passing with great regularity and exactness to the lip or 
margin of the cup. 
These singular bodies have been a great puzzle to me. I was at first 
disposed to consider them otoliths, but better-preserved specimens showed 
the hour-glass structure with the central perforation and the regularly radi- 
