﻿232 ANTTAKCITA. 



36483. Ventral aspect of trunk and right appendage. 



Purchased. 1862. 



36464. Anterior ventrolaterals and imperfect appendages. 



Presented by G. E. Roberts, Esq., 1862. 



P. 196. Trunk and appendages, ventral aspect. Weaver- Jones Coll. 



P. 197. Three portions of ventral plates, one being in counterpart. 



Weaver-Jones Coll. 



The two species mentioned below are founded upon anterior 

 median dorsal plates, of which there are no examples in the Collec- 

 tion . The type specimens are preserved in the Museum of Columbia 

 College, New York. 



Bothriolepis leidyi, J. S. Newberry, Palaeoz. Fishes N. America 

 (Mon. U.S. Geol. Surv. no. xvi. 1889), p. Ill, pi. xviii. 

 fig. 2, pi. xx. figs. 1-5 : Stenacantlvus nitidus, J. Leidy, 

 Proc. Acad. Nat. Sci. Philad. vol. viii. 1857, p. 11, and Journ. 

 Acad. Nat. Sci. Philad. [2] vol. iii. (1856), p. 164, pi. xvi. 

 hgs. 7, 8. [Type of Stenacanthus, founded upon portion 

 of pectoral appendage in Mus. Acad. Nat. Sci. Philad.] 

 Holoptychius americanus, J. Leidy (in part, errore), ibid. 

 1856, p. 163, pi. xvii. fig. 4. — Catskill Group (Upper 

 Devonian) ; Tioga Co., Pennsylvania. 



Bothriolepis minor, J. S. Newberry, op. cit. (1889), p. 112, pi. xx. 

 figs. 6-8. — Chemung Group (Upper Devonian) ; Brad- 

 ford Co., Pennsylvania. 



In the singular groups of detached plates of Bothriolepis leidyi, 

 the large anterior median dorsal plate is more numerous than any 

 of the others. This reminds the English palaeontologist of the 

 manner in which the shields of Pteraspis sometimes occur in groups 

 in the Cornstones of Herefordshire — one group comprising all dor- 

 sals, another all ventrals. The last-named circumstance has some- 

 times been regarded as proof that the so-called " Scaphaspis " is 

 not the ventral plate of Pteraspis ; but in this case, as in that of 

 the American Bothriolepis,th.e arrangement of the fossils iy evidently 

 due to drifting and assorting by currents of water during the depo- 

 sition of the sediment. 



