FISHES OF THE DEVONIAN AGE. 47 
Chimeroids are only the remnants of an expiring fauna, it was to be expected that 
the life of this fauna would be found to reach far back in time; and it was quite con- 
sistent with all the facts before known to find traces of Chimroids in Paleozoic rocks. 
The Rays, on the other hand, are apparently a comparatively modern off-shoot 
from the original Sclachian stock. We have no evidence of their existence at a period 
anterior to the Jurassic age, and they are evidently now in their epoch of fullest 
development; while the Chimzroids, in their decadence, should naturally have had 
an earlier birth. 
Since these notes were written Sir Philip Egerton has said in a letter 
to me that he had no doubt of the affinities of the fishes which bore the 
teeth of Rhynchodus with the Chimeroids of the present day, and as he has 
studied this family more carefully than any other naturalist, this conclusion 
will probably not be questioned. 
Quite recently I have received from Mr. Thomas A. Greene, of Mil- 
waukee, Wis., a number of fragments of the teeth of a large species of 
Rhynchodus, obtained by him from the hydraulic limestone quarries in the 
vicinity of that city. On another page I have described these remains and 
named the species after the discoverer. From Prof. 'T. C. Chamberlin, State 
geologist of Wisconsin, I have received a tooth of another and smaller 
species, found in the Hamilton rocks of Brown Deer, Wis. ‘This species I 
have called Rhynchodus excavatus, and have briefly described and figured it 
in another part of this memoir. 
Ruayncuopus secans, Newb. 
Plate XXVIII, Figs. 1-3. 
Rhynchodus secans, Newb; Paleontology of Ohio, vol. 1, p. 310, pl. 28, fig. 1. 
Teeth somewhat semi-circular in form, posterior angle rounded or 
obtuse, the anterior prolonged into a more or less acute point; posterior 
and inferior margins thin and sharp, anterior and superior margins thick- 
ened; lateral surfaces smooth, almost polished; interior face flattened, ex- 
terior sloping from the anterior and upper thickened edges to the thin mar- 
gins behind and below; upper margin nearly straight; anterior haif often 
worn to a sharp, knife-like edge by contact with the corresponding edge of 
the opposite and overlapping tooth. 
Of these singular teeth I have quite a number from the upper portion 
of the Corniferous limestone at Sandusky and Delaware, Ohio. In outline 
