54 MOSASAURUS. 



2. A fragment, apparently from tlic 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 canities, 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-aheolar 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 

 tlic 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 Covnity, 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 Mosasam-us. It is perfect, 

 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. The 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 c/indition are visible on 

 the anterior ridge. The outer surface of the crown is nine lines wide at the bottom 



