10 
FOSSIL REPTILIA OF THE 
mesiad, and overlapping the mastoid (s) and tympanic (28), is the longest, and termi- 
nates in a point : the surface of the hone is smooth- 
The temporal fossae are broader than they are long. At their forepart the parietal 
side-wall of the cranium expands as it advances, and is continued into the postfrontal 
or postorbital partition. 
The orbits are rounded anteriorly, and both the upper and under parts of the frame 
make an angular junction with the straight hinder part. 
I The nostrils have the usual small size and baekward position. 
In both orbits some of the thin sclerotic plates of the eyeball {s, s) are preserved ; 
this is the first specimen in which I have had evidence of this structure. 
The interlocking of the teeth of the upper and lower jaws, through the singular 
care and skill devoted by Mr. Harrison to the removal of the matrix, is peculiarly well 
displayed in this instructive fossil. 
The foremost tooth in each premaxillary make a pair, which curve forward and 
downward between the two foremost teeth of the lower jaw, the premaxillary teeth 
slightly diverging as they descend. Tab. Ill, fig. 3. The succeeding premaxillary 
teeth, four in number, alternate with mandibular ones. I cannot make out with 
certainty the maxillo-premaxillary suture, but the fifth tooth, counting backward, seems 
to be near to or upon it. The second premaxillary tooth is double the size of the firs. ; 
the third, fourth, and fifth gradually diminish ; the sixth (first maxillary ?) is small ; the 
seventh tooth suddenly resumes the size of the second ; and the eighth, of nearly equal 
size, curves down close to the seventh, and the two are interposed between the inter- 
space of opposite mandibular teeth. From four to five smaller teeth are traceable 
behind the eighth, and there may have been more in the upper jaw. 
Of the lower jaw ten teeth are shown on each side ; the second, third, fourth, and 
fifth are the longest and largest, as in Tab. II. In general, the teeth of the upper jaw 
are separated by intervals allowing the passage of those of the lower ; the teeth of the 
foremost premaxillary pair being closer together ; and those of the foremost mandi- 
bular pair being wider apart. They all present the usual generic character of crown — 
long, slender, curved, pointed, circular in transverse section, wdth the enamel finely 
but definitely ridged longitudinally. The longest exserted crown measures ten lines, 
the shortest four lines, the thickness being in proportion. 
The true number of the teeth in the lower jaw is yielded by the specimen of the 
dentary bone. Tab. Ill, fig. 2, in which twenty-five alveoli are shown on one side, and 
twenty-four on the other. The size of the alveoli, and the extent of their interspaces, 
are greatest at the anterior half of dentary. The small successional teeth at the 
posterior part of the series are so advanced as to look like a double row at that part. 
A longitudinal groove or depression at the inner side of the base of the alveoli lodged 
the thicker mass of the vascular gum overlying the matriees of the successional teeth. 
The skull of the Flesioscmrm dolichodeirus is broad in proportion to its length, with 
