20 PALEOZOIC FISHES OF NORTH AMERICA. 
Pennsylvania the remains of organisms similar to those that had been be- 
fore discovered in the Ludlow rocks of England. He published’ a paper on 
the discovery of Pteraspidian fishes in the Upper Silurian rocks of North 
America, and in it he describes two species of Palwaspis—P. Americana and 
P. bitruncata—which he states had been obtained from the Bloomfield sand- 
stone, the upper member of the Onondaga salt group. This would make 
them somewhat older than any similar fossils found in the Old World. 
In addition to these bucklered fishes, Professor Claypole describes in the 
same paper two minute spines which he considers those of Elasmobranchs. 
One of these was obtained from the Bloomfield sandstone; the other from a 
still lower horizon, the Clinton group. ‘These spines are very small, not 
more than half an inch in length, and broken at both ends; they cannot, 
therefore, be made the basis of any positive statement or wide generaliza- 
tion. It is perhaps not certain that they are not the spines of crustaceans, 
such as were obtained by the geologists of New York from the Clinton 
group in that State and named Onchus Deweyi, and at one time supposed to 
be the defensive organs of fishes. I am, however, disposed to coincide with 
the view of Professor Claypole, although the ichthyic character of these 
little objects cannot be asserted until proven by more complete specimens. 
The question may be definitely settled, however, by the discovery of one 
spine which shows the proximal extremity. If this should prove to be solid 
and more or less roughly pointed, we may be quite sure that these are the 
dorsal spines of fishes; but if irregularly expanded, forming a rim about a 
central cavity, then we must conclude they were the appendages of crusta- 
ceans. The so-called Onchus Deweyi from New York has been shown to 
have belonged to a crustacean, and yet a fragment of the upper end of one 
of these objects would be naturally taken as a portion of a fish spine. 
Special interest attaches to these earliest traces of fishes, and it is to be 
hoped that those who may have opportunity for continuing Professor Clay- 
pole’s researches will not fail to improve it, and if possible add to the small 
but most important group of relics he has described. | 
1 Quart. Jour. Geol. Soe. London, 1585, vol. 41, p. 48. 
