FISHES OF THE CARBONIFEROUS SYSTEM. 183 
are based on teeth and spines which, separating from the cartilaginous jaws 
and perishable integuments, were with the dermal tubercles scattered broad- 
cast over the sea bottom. In these circumstances it is evident that the 
number of species has been exaggerated by giving different names to spines 
and teeth which once belonged together. It is also probable that the species 
have been multiplied by assigning distinct names to the teeth of different 
forms which once belonged to a single dental series. Among the Cestra- 
cionts, which include a large part of the Lower Carboniferous Elasmo- 
branchs, there is a marked difference between the teeth of the symphysis 
and those which cover the posterior portions of the jaws; hence it is possi- 
ble that we have as yet obtained from this formation traces of not more 
than three hundred different kinds of sharks. This, however, forms a richer 
Elasmobranch fauna than that which inhabits our present seas; the num- 
ber of living species of Sharks, Rays, and Chimeras being, according to 
Dr. Gunther, only about two hundred and eighty. 
Although we probably have as yet but a fraction of the fish fauna 
of the Carboniferous seas represented in our collections, we certainly 
have enough to give us a good idea of its zoological character and rela- 
tions. 
In reviewing the material before us we find an almost total absence of 
the Placoderms and sealed Ganoids, which gave character to the fish fauna 
of all bodies of water, salt or fresh, in the Devonian age. Comparing the 
fishes of the Corniferous with those of the Mountain limestone, the differ- 
ence is surprising. In the first are many dermal tubercles, some spines 
(Macheracanthus), and very rarely one of the pavement teeth of a conchiv- 
orous Shark; the greater part of the remains being those of Placoderms and 
Ganoids. In the Carboniferous limestone, on the contrary, the spines and 
teeth of Sharks are found in infinite variety, but scarce a plate or scale to 
record the presence of a Placoderm or a Ganoid. ‘These were, however, 
not wanting to the fauna of the age; for, as we have seen, along the shores 
and in the bays where the Waverly strata were deposited—to a large degree 
synchronous with the lower beds of the limestone—we find abundant 
remains of the great Placoderms—Dinichthys, Titanichthys, etc—and where 
the conditions were favorable, of many little Paleeoniscoid fishes. But all 
