17 
lar extremity. The latter looks partly downwards, and is divided by a 
deep groove above into two parts representing the usual condyles. One 
of these is comparatively depressed, while the other has a massive superior 
crest, which makes its long axis vertical instead of horizontal, as is that 
of the other condyle. 
There is considerable resemblance between this femur and that of 
Dimetrodon gigas, and ina less degree to that of Clepsydrops natalis, but 
both the latter have well developed condylar surfaces. They are also 
larger in proportion to the size of the rest of the skeleton, in the Pelycosau- 
rians mentioned. 
Further characteristics of this genus and of the species it embraces will 
ke given at a future time. 
TRIMERORHACHIS Cope. - 
American Naturalist, 1878, p. 328 (April 22). Proceedings American 
Philos. Society, 1878, p. 524. 
This genus, as has been pointed out, differs from Hvyops in the super- 
ficial character of its vertebral ossifications, and in the absence of ossified 
neural spines. 
A well-preserved cranium, and portions of several others referrible to 
this genus, furnish characters which have been hitherto inaccessible. They 
probably belong to the Z. insignis, but this is not certain. 
Generic Characters, ete.—The type of skull is that of the order of Stego- 
cephali generally. The superior walls are thin, and are sculptured on the 
superior surface. The mucous grooves are distinct, but do not form a 
well-defined lyra. There is a groove which is parallel to the anterior 
borders of the orbit fora short distance, and which then turns forwards 
and then inwards. The dermal ossification is distinguished from that of 
the maxillary bone by a squamosal suture. A mucous groove descends to 
it obliquely forward from the superior quadrate region, and sends a branch 
at right angles to its anterior extremity to a point posterior to the orbit. 
Of superficial ossifications, the boundaries are difficult to determine, owing 
to the obscurity of the sutures. Enough can be seen to demonstrate the 
presence of supramaxillary, epiotic, and supraoccipital dermal bones. The 
nostrils are large aud well-separated, and look upwards. 
The teeth are acute, and of subequal size; their superficial layer is 
deeply inflected at the base. 
The parasphenoid bone is wide posteriorly, but contracts abruptly, and 
extends forwards on the middle line. Owing to crushing of a part of the 
surface, I am unable to ascertain its anterior, or vomerine suture. The 
basifacial axis bone is quite narrow, and is edentulous. It is connected with 
the superior cranial walls by a vertical osseous plate on each side, which 
may represent alisphenoid, orbitospheuoid and ethmoid. The palatoptery- 
goid arch is a longitudinally extended sigmoid, enclosing with the axial 
elements, an enormous choanoérbital foramen. It extends from the 
middle line below a short distance posterior to thé position of the nostrils 
