Claypole.] "^^ [April 6, 



the anterior angle where its breadth is nothing and widening to the lateral 

 angles where its breadth equals half an inch. The outer line of this mar- 

 gin between the lateral and basal (?) angles is straiglit, giving its greatest 

 breadth about the middle of these sides where it equals an inch. The 

 margin of the basal side is about three-quarters of an inch in breadth in 

 the middle. The whole of this margin is verj^ finely striate nearly at right 

 angles to the sides of the plate. 



This margin is evidently the portion of the plate which was overlapped 

 by the adjoining plates and in this respect the resemblance between it and 

 the ventro-median plate of Pterichthys oUongus Ag. is obvious. 



The outline of the plate corresponds very closely with that of the dorso- 

 median plate of Pteriehthys, and were it not perfectly flat I should be in- 

 clined to refer it to that part of the exo-skeleton. But this flatness renders 

 it more probable that it represents the ventro-median or well known 

 "lozenge-plate" of Hugh Miller— the central piece of the armor of this 

 fish on the lower side — overlapped on all sides by others. 



Prof. Whiteaves has very kindly lent me for comparison the original 

 and only specimen of the ventro-median plate of his new species, Coccosteus 

 Acadicm. This, much more closely than my specimen, resembles the 

 ventro-median plates of Pteriehthys and Coccosteus, as given by Hugh 

 Miller in his "Old Red Sandstone." It is quadrilateral, with two out- 

 wardly concave and two straight sides. The ornamentation is very pecu- 

 liar, the plate being "quartered " if we may borrow an expression from 

 heraldry, and having crenulated ridges parallel to the outer side in the first 

 and fourth quarters and irregularly scattered tubercles in the second and 

 third. Altogether it shows little resemblance to the plate here described. 



Prof. Newberry remarked in his letter that he very much doubted if the 

 plate here described belonged strictly to Pteriehthys and was inclined to 

 consider it the type of a new genus. Probably this will be the result of a 

 better knowledge of its structure, but it would be premature in this note to 

 found a new genus on the fragments already known. When other parts of 

 the exo-skeleton have been found it will be time to consider its generic 

 position. Meanwhile I suggest for it the provisional name, Pterichthys 



RUGOSUS. 



The accompanying figure is taken from a photograph and will suffice to 

 preserve the appearance of the specimen for future comparisons in the 

 event of its loss or destruction. 



0)1 the Kiiuismhll White Sundstone. By E. W. Claypole. 



{Read before the American Philosophical Society, April 6, ISSS.) 



Near the base of the red sandstones and shales which compose the Great 

 Ponent series of Professor Rogers, lies a thin bed of white sandstone which 

 promises to be of much interest, and perhaps of some importance in the 



