from the Shales of the Northumberland Ooal-field. 269 
must be placed considerably. apart from each other, and not 
much in advance of the posterior margin of the nasal bone ; at 
least it is only a short way in front of the posterior mucus- 
groove. 
There are five or six conical teeth in each premaxillary ; 
they are stout, grooved, and circular at the base, with the 
crown compressed in the direction of the length of the jaw; 
they are provided with. wide cutting-edges, and are rather 
abruptly pointed. The largest are upwards of half an inch in 
length, Gating for their lost apices. The three anterior are 
much larger than the rest, and they are placed at some little 
distance apart, there being large depressions between them in 
the alveolar groove, apparently for the reception of the crowns 
of the mandibular teeth. The two or three posterior teeth are 
comparatively small, and are placed nearer together than the 
anterior. 
T'wo specimens of the anterior portion of the left mandible 
have also occurred, the largest and best preserved of which 
is four inches long and about two and a quarter inches wide. 
The surface exhibits the same ornamentation as the other 
bones. The symphysial surface is perfect; it is considerably 
longer than the width of the ramus, being extended by a pro- 
cess from the inner or lower margin of the bone; there is a 
trace of a mucus-groove along the inferior border of the ramus. 
None of the teeth in these specimens are perfect; but enough 
is left to show that they are similar to those already described. 
The first tooth is small, and is placed close to the symphysis ; 
the second is very large, and is immediately behind the first ; 
it is half an inch in diameter at the base; a large depression, 
five-eighths of an inch wide, succeeds this, and then four small 
teeth placed close together, the two posterior of which are 
larger than the anterior pair; but one of them is indicated 
only by a mere fragment of dentine ; then comes another large 
depression, half an inch wide, but whether or not this is for 
the reception of the crown of a maxillary tooth, or is the im- 
pression of the base of a tooth belonging to the mandible, it is 
difficult to say. Close to this depression is the base of another 
tooth equal in size to the large anterior one. At this point the 
‘alveolar groove is broken away; and shortly after, the fragment 
of the ramus terminates. The alveolar groove is distinctly 
defined, but widens inwardly to accommodate the bases of the 
large teeth, which consequently have the appearance of being 
— within the smaller ones; they form, however, with the 
atter only a single row, and the outer borders of all are placed 
on the same external line. The other ramus is very imper- 
fect ; but, as far as they are traceable, the teeth have the same 
arrangement. : 
