FISHES OF THE CARBONIFEROUS SYSTEM. 93 
reconstruct the defensive armor. Probably the central plate of the plastron 
was surrounded by four others, as in Coccosteus and Dinichthys. Of the 
plates of the upper surface of the body we have as yet little knowledge. 
Whether the body was protected above by one great dorsal plate, as in 
Dinichthys, or by six or more articulated together, as in Pterichthys, we can 
not say, but some of the plates which have been found may perhaps have 
been located on the back. 
More material will be required before we can decide in regard to the 
affinities of this fish, but since we have failed to find any trace of a dorsal 
shield resembling that of Dinichthys, the strongest plate in the armor and 
the most likely to be preserved, we may infer that the protection of the 
upper side of the body, like that below, was furnished by several overlap- 
ping and relatively small and thin plates. 
Prof. E. W. Claypole, who described! the middle ventral plate of this 
fish, has referred it with doubt to Plerichthys; but this was a much larger 
fish than any known species of that genus and had a dermal armor com- 
posed of plates of different shapes from those of Pterichthys and ornamented 
ina distinct and peculiar way. Many years before Professor Claypole 
published the notice of his Pterichthys rugosus I had received fragments of 
different plates of this fish and had written a partial description of them, 
giving to the genus the name now used. Feeling it necessary to separate 
the genus from Pterichthys, I have thought best to retain the name then 
chosen as expressive of its most striking character, retaining Professor Clay- 
pole’s name for the type species described below. 
Hotonema RuGOSA, Claypole, sp. 
Plate XVII, Figs. 1-4. 
Pterichthys rugosus, Claypole; Proc. Am. Philos. Soc., vol. 20, 1833, p, 664. 
In the Chemung rocks of New Jersey and northern Pennsylvania it is 
not uncommon to meet with fragments of flat and relatively thin plates of 
bone, which’ evidently once formed part of the defensive armor of a Placo- 
derm fish. These fragments are usually covered with an ornamentation 
1Proc. Am. Philos. Soc., vol. 20, 1883, p. 664, 
