so 
APPENDIX. 
backwards, obtuse, with a faint median longitudinal groove. Posterior 
face at the tip ot the tooth oblique ; no striae. 
Length 26.7 lines; width 4.5 lines ; depth at base 3 lines. 
This species is much more slender than the P. agassizii, Gibbes , the 
only species which resembles it. Found by Prof. W. C. Kerr, State 
Geologist of North Carolina, at Flowers’ marl pit, Duplin county, North 
Carolina. 
ACTIN OPTERI. 
Amblypteros ornatus. Emmons, N. Amer. Geol. 44, fig. 16. Trias. 
Rhabdolepis speciosus. Emmons , 1. c. 45, fig. 17. Triassic beds. 
Pycnodus carolinensis. Emmons, Geol. North Carolina, 1S56. Mio- 
cene, Duplin county. 
PNEUMATOSTEUS. Cope. 
This genus is established on a caudal vertebra of a fish nearly allied to 
the gars ©f North America. It is opisthocoelian, and without trace of 
suture of either neural or haemal arches. The elements constituting the 
haemal arch appear to be diapophyses ; they are divergent, and probably 
do not unite distally ; they are directed more posteriorly than anteriorly. 
Their proximal boundary is apparently indicated by an indistinct eleva- 
tion, perhaps the position of the original suture. The neural arch is 
split above by a deep median anterior fissure, on each side of which the 
narrow zygapophyses diverge. There is no zj’gantrum. The base of the 
broken neural spine is very small, and is as long as wide; it may probably 
have had but little elevation. 
The structure ot the hone is exceedingly light, and the external osseous 
layer very dense. In order to reduce the weight consistently with the 
size, the lateral and inferior faces are excavated by deep concavities termi- 
nating in pits. There are two on each side separated by a longitudinal 
ridge like septum, which is plane with the expanded rims of the cup and 
ball. The superior pits are beneath the base of the neural spine, and 
nearly meet under the floor of the neural canal. The inferior concavity is 
very large, and extends from rim of cup to ball, and is divided longitudi- 
nally by a thin laminar hypapophysis. The bases of the diapophyses are 
wide, and extend from the base of the ball three-fourths the distance on 
each side to the rim of the cup. 
The form of the vertebra is compressed. The ball is more convex 
transversely than vertically, and presents a slightly double convexity in 
profile. This is produced by a slight transverse contraction of the inferior 
