Gal MOSASAURUS. 
2. A fragment, apparently from the forepart of the lower jaw, containing the 
fangs of four teeth, from Burlington County, New Jersey, presented to the Academy 
of Natural Sciences by Dr. S. G. Morton. The fragment is ten inches long, and 
was sufficient to accommodate six teeth. At its widest part, opposite the position 
of the fifth tooth from the anterior extremity, it measures two inches and a half. 
The inner and outer surfaces are straight longitudinally and convex vertically. 
The outer surface, about an inch and a half from the alveolar edge, and near the 
broken border of the specimen, presents a transverse row of four large vasculo- 
neural foramina, communicating with the remains of the dental canal within. 
The four fangs of teeth, contained in the specimen, are about three inches in 
length, of which about three-fourths are inserted within alveoli. The exserted or 
extra-alveolar portions of the fangs form truncated cones at the border of the jaw 
surmounted by the fractured borders of the lost crowns. The loss of the latter has 
exposed the base of the large interior pulp cavities, which measure from half to 
three-fourths of an inch in diameter and extend in an inverted conical manner 
within the fangs. 
At the border of the jaw, the bases of the extra-alveolar portions of the fangs 
range in transverse diameter from fourteen to twenty-two lines. 
The intra-alveolar portions of the fangs are cylindroid, moderately curved, and 
terminate in rounded extremities just internal to the position of the dental canal. 
The first and third fangs of the specimen are loosely inserted in their sockets, 
with which they appear never to have been coossified. The second and fourth fangs 
are firmly coossified with their alveoli, and are deeply excavated postero-internally 
into large cavities which accommodated successional teeth, but which are lost from 
the specimen. 
The second, third, and fourth fangs are separated by thin osseous partitions of 
the alveoli. 
The fourth fang presents in its postero-internal part a small cavity for a succes- 
sional tooth. 
The first fang encroached so much on the position of the second as to have 
depressed its anterior part. It presents the remains of a very small cavity for a 
successional tooth in the same position as the other fangs, and exhibits what 
appears to be a portion of a second and larger one at the forepart. 
3. A tooth, from Monmouth County, New Jersey, loaned to me for examination, 
from the collection of Rutger’s College, by Prof. Cook. The specimen, represented 
in Fig. 2, Plate X, resembles the tooth in the jaw fragment first described, or is of 
the form which is usually viewed as, characteristic of Mosasaurus. It is pertect, 
except that the apex and anterior carinated ridge of the crown are worn, and it 
measures five inches and a half in length. 
The length of the enamelled crown in its present condition is twenty-two lines ; 
the antero-posterior diameter at base thirteen lines, and the transverse diameter 
fourteen lines. 'he outer and inner surfaces are defined by acute, linear ridges, 
which become more carinated towards the apex of the crown. The unworn poste- 
rior ridge is minutely denticulated, and traces of the same condition are visible on 
the anterior ridge. The outer surface of the crown is nine lines wide at the bottom 
