FISHES OF THE CARBONIFEROUS SYSTEM. 109 
pierced by minute orifices; in short, precisely the surface markings shown 
in the figures and descriptions given by Agassiz in his Old Red Sandstone 
Fishes. The armor of the upper side of the body consisted of a series of 
polygonal scutes, which have never yet been found in position, and there- 
fore nothing positive can be said in reference to their number and arrange- 
ment. In Tioga County, Pa., Mr. Andrew Sherwood has obtained at one 
locality hundreds if not thousands of these plates of Bothriolepis Leidyi, 
crowded together as though they had been the numerous scales of some 
relatively large fish. According to Eichwald the body of Bothriolepis 
was covered with scutes, which he supposed to have been arranged in 
rows like the plates of the sturgeon, and such was the belief of Agassiz; 
but in the important paper “On the Structure and Classification of the 
Asterolepidée,” published by Dr. R. H. Traquair in the Annals and Maga- 
zine of Natural History for December, 1888, Bothriolepis is described as 
haying essentially the same structure as Pterichthys, and differing from that 
genus only by a few minor characters, which render it rather difficult to 
distinguish them. The material yet obtained in the United States, all of 
which I have passed in review, is too fragmentary to give much assistance 
in the settlement of this question; but it is quite certain that where hun- 
dreds and thousands of fragments of the defensive armor of Bothriolepis 
occur, as they do in the Catskill of Tioga County and the Chemung of 
Bradford County, Pa., individuals ultimately will be found in so good pres- 
ervation as to harmonize the diverse views which have been entertained in 
regard to these singular fishes. 
One remarkable feature in Bothriolepis is the peculiar joint by which 
the pectoral spine articulates with the body, and which shows essentially 
the same structure that we find in the Siluroids of the present day. 
Most persons are familiar with the complicated and effective articula- 
tion of the pectoral fins in our catfishes (Amiurus). The arched head of 
the spine moves freely in a groove through an are of about ninety degrees, 
and is protected by guards, which prevent lateral motion and fix it firmly at 
the will of the fish at the point of greatest possible extension from the body. 
In some of the Siluroids it is impossible to separate the spine from its socket 
without fracture, even when the soft parts have all been removed. The 
