EASTMAN: THE DINICHTHYIDS. 27 
specimen is too imperfect to admit of a precise determination of the 
several elements, as the author has informed us by letter. 
The only other instance recorded where the plastron has been pre- 
served in situ, is that made known by the writer at the Buffalo Meeting 
of the American Association for the Advancement of Science. For the 
discovery of this interesting fossil, science is indebted to Mr. F. K. 
Mixer, Curator of the Buffalo Society of Natural Sciences, who found 
the slab in place at the bottom of a small stream bed near Sturgeon 
Point, on the lake shore, twenty miles west of Buffalo, N. Y. The 
horizon at this point is the black Portage Shale, which has already 
yielded a considerable number of fish remains.’ The plates were cor- 
rectly determined by Mr. Mixer to be of Dinichthyid nature, and were 
so. labelled by him and placed on exhibition in the Museum of the 
Buffalo Society. To this enthusiastic collector the writer is greatly in- 
debted for the privilege of studying the specimen, and of presenting the 
following description of it. 
Although the fossil has suffered considerably from aqueous and 
atmospheric erosion, the salient features have been so far preserved as to 
furnish points of control sufficient for reconstructing almost the entire 
topography. The slight extent to which the diagram given in Plate 1 
has been reconstructed may be seen from a comparison with a photo- 
graph of the actual fossil, reproduced in Plate 4. In most cases the 
sutural indications are so distinct, and continuous over such an area, 
that we have only to produce them in the same general direction across 
breaks in the surface until they meet, in order to complete the small 
portions that are interrupted. Thus, among the prominent landmarks 
that are left may be mentioned the terminal angles of the antero- 
ventro-laterals, which overlie the postero-ventro-laterals in their natural 
position. Half way between these points gives us the median line of the 
body ; and as all the plates are arranged symmetrically with reference to 
it, it is clear that the fossil has been in no wise distorted. A knowledge 
of this fact permits us to supply the contours of one side from informa- 
tion derived from the other, and fortunately the two sides supplement 
each other to a remarkable degree. The only boundary lines that are 
not tolerably distinct are the forward portions of the antero-ventro- 
laterals. We will consider the relations of the different plates in order. 
Ventro-Median Plates. —The first question that arises concerning the 
median ventrals is whether they are represented by one element or by 
` Mixer, F. K., Amer. Geol, Vol. XVII. p. 228, October, 1896. Williams, 
H. U, Bull. Buffalo Soc. Nat. Sci, Vol. V. pp. 81-84, 1886. 
