﻿THE CARBONIFEROUS AND DEVONIAN FORMATIONS. 163 



furnished with coarse, longitudinal, flexuose, anastomosing ridges or tubercles. Ven- 

 tral fins on each side, posterior to the middle j dorsal fin opposite the anal fin, which 

 is close to the caudal fin ; pectorals small. 



HOLOPTYCHIUS AMERICANUS, Leidy. 



Holoptychius nobilissimus, Ag., Hall, Geol. of New York, pt. IV, 281, fig. 130. 



By this name I propose to distinguish the remains of the genus which have been 

 discovered to the present time in Pennsylvania, although it may possibly include two 

 species. Remains of Holoptychius are stated to be quite abundant in certain localities 

 of the Old Red Sandstone Formation of Tioga county ; but such as they are, consist- 

 ing of isolated scales, cranial bones, and teeth, they are so exceedingly friable and 

 the matrix so hard, or so soft and brittle that it is difficult to obtain specimens suf- 

 ficiently perfect to be characterized. Among numerous specimens, for the most part 

 consisting only of impressions left by the disintegration of the remains, presented to 

 the Academy, by Timothy Conrad, Esq. and Charles E. Smith, Esq., there are a few 

 which I have ventured to describe, and which are represented in figures 9, 10 of plate 

 16, and figures 1-4 of plate 17. • 



One of the specimens, represented in figure 9, plate 16, is a portion of a large scale,, 

 with an impression of a portion of the remainder. It measures nearly 2 J inches in 

 length, and apparently has been ovally rhombaidal in its perfect condition. The 

 covered portion of the scale constitutes nearly one half, and is smooth. The exposed 

 surface of the scales, as indicated hy the impress of the matrix, was furnished with 

 coarse, longitudinal, flexuose, and somewhat ramifying ridges. 



A smaller scale, represented in figure 10, plate 16, of which specimens are more 

 frequent than of the preceding, is 14 lines long and 12 lines broad, and is a rounded 

 square. A little more than half its surface has been covered by the scale in advance ; 

 and the exposed portion of the surface is covered with coarse longitudinal ridges. 

 This scale resembles an isolated specimen of one from Holoptychius nobilissimus, repre- 

 sented in figure 26, plate 31 a, of Agassiz' Poissons Fossiles, but is not at all like those 

 represented in plate 23 of the same work. 



The impression of a tooth, left in a portion of matrix by the destruction of the original, 

 from which a clay cast wa's taken, gives the form characteristic of the large teeth of 

 Holoptychius, as represented in figure 1, plate 17. The tooth has been ten lines long 

 and four lines in diameter at the base. It is conical, circular in transverse section, as 

 represented in figure 2, plate 17, and is folded two thirds of its length from the base.. 



A very imperfect fragment of a maxillary bone, consisting indeed of little more than 



the thin internal surface adhering to a portion of matrix, represented in figure 3, plate 



17, exhibits at the anterior extremity the remains of a large tooth, partially consisting 



only of its impression ; and further back at the margin of the bone it presents two 



conical denticles about one line long. 



42 



