﻿162 LEIDY'S DESCRIPTIONS OF REMAINS OF FISHES FROM 



Timothy Conrad borrowed from the cabinet of Charles A. Poulson, Esq., for mv in- 

 spection. It was presented to the latter gentleman by Townsend Ward, Esq., who, in 

 a note, observes, it was given to him " by the engineer of the stationary engine at the 

 head of inclined plane number 3 of the old portage railroad," which crossed the 

 Alleghany Mountains from Hollidaysburg, in Blair County, Pennsylvania. Mr. Ward 

 further states, "it was obtained from a stratum about one foot thick, black, carboni- 

 ferous, and calcareous, which was exposed by the excavation for the buildings to 

 accommodate the stationary engine." He then adds, " I obtained quite a number of 

 other fossils there, and from the same stratum near Freeport, above Pittsburg, and I 

 think on the Conemaugh, seventeen miles west of Johnston. I found the stratum 

 distinctly marked at these different localities, and have understood it is alsotobeseen 

 in Ohio, where it is as distinctly marked by its appearance and fossils. It is in the 

 bituminous coal series, and has a coal seam beneath it." 



The tooth is of an iron gray color, hard, well preserved, and perfect, except that the 

 basal angles of the crown and the end of the fang are broken away. 



The crown has the form of one half of a broad, compressed cone. Its outer side 

 is smooth, and transversely convex, but slopes in a nearly even plane from the tren- 

 chant margins. The inner side is also smooth, and forms a vertical plane from the 

 latter position, and is transversely concave. The trenchant edges, except at the basal 

 angles, are nearly straight, and are minutely serrulated, or rather simply striated. 



The basal cingulum surrounding the crown is bow-shaped on each of the broad 

 sides ; and it is composed of about nine imbricating, parallel folds. Externally it 

 slopes inwardly beneath the crown ; and internally it forms a thick convex ridge de- 

 scending much below its position externally. 



The fang is an osseous plate, thick at the middle and towards the broken end, but 

 thinning towards the lateral borders, which are slightly bent, scroll-like, from within 

 outwardly. The inner surface is transversely concave ; the outer one is convex, and 

 presents a wide groove following the course of the basal cingulum. 



The measurements of the specimen are as follows : Breadth of the crown (not en- 

 tire) 14 lines; height, including the basal cingulum, internally Hi lines, externally 

 9 lines. Breadth of the fang lOi lines; length (not entire) internally 4J lines, ex- 

 ternally 7 lines. 



Plate 16, figs. 4, 5, 6. — Outer, inner, and lateral views of a tooth of Petalodus alleglianiensis. 



HOLOPTYCHIUS, Agassiz. 



Generic Characters. — Body broad, short, compressed. Tail heterocercal, short. 

 Head flat; the bones rough, or irregularly granulated. A few large conical teeth 

 folded at the base, and numerous small conical, intermediate ones. Scales large, 

 more or less rounded, rhomboidal ; the covered portion smooth ; the exposed surface 



