94 PALEOZOIC FISHES OF NORTH AMERICA. 
which consists of raised enameled lines, often simple and parallel, but some- 
times broken and somewhat tortuous. 
In 1865 I received from Prof. Edward Orton a nearly complete plate 
of a comparatively small individual belonging to this species. It had been 
obtained by him from the Chemung rocks of Franklin, Delaware County, 
N. Y. This was a posterior lateral plate of the ventral series. Subsequently 
I found in the State cabinet at Albany, New York, numerous fragments of 
plates marked in the same manner, but none sufficiently well preserved to 
permit a restoration of the complete outlines. From Mr. A. T. Lilley, of Le 
Roy, Bradford County, Pa., I have recently received a considerable number 
of such fragments, several of which are represented on Plate XVII. The 
largest portion of any plate yet found, except that figured by Professor 
Claypole, is that represented in Fig. 1, the original of which is now in the 
geological collection of the American Museum of Natural History. For 
the privilege of reproducing it I am indebted to the courtesy of Prof. R. P. 
Whitfield. This is plainly a lateral plate, but whether of the upper or under 
surface is not certain. That it is a lateral plate may be inferred from its 
lack of symmetry and the fact that it nowhere shows the beveled margins, 
indicating overlap, so characteristic of the central plates in this and other 
related fishes. 
The surface markings of the plates of this fish are so peculiar, that they 
will be recognized wherever found, and it is hoped that the figures now given 
will prompt collectors to search for material which will permit its complete 
restoration. 
In Fig. 2 I have copied Professor Claypole’s photograph, given in the 
Proceedings of the American Philosophical Society. It is reproduced by 
photo-engraving, and may therefore be accepted as truthful. It is of about 
half natural size; the original, of which Professor Claypole has kindly sent 
me a cast, was not arched, but quite flat ; from which, as well as from its form, 
I infer it was the central plate of the plastron, and to be compared with the 
lozenge-shaped plate of Coccosteus; the ventro-median plate of Owen. 
Since the above notes were written I have received from Professor 
Claypole a cast of another plate of Holonema rugosa, said to have been found 
in the Catskill rocks of Bradford County, Pa. It is a lateral plate, much 
