MOSASAURUS. 



55 



and eight lines at the middle. It forms less than one-sixth of a circle, whose radius 

 is about eight lines, and is irregularly subdivided into four planes below, extending 

 into three towards the apex. The inner surface forms about three-fourths of a circle, 

 whose radius is six lines, and is irregularly subdivided into 

 eleven planes. The circumference of the crown at the enamel ^°" ^' 



border is three inches and three-quarters, of which the inner sur- 

 face is two inches and eleven lines, the outer surface ten lines. 

 The accompanying outlines. No. 1, represent transverse sec- 

 tions of the crowTi at its base, a short distance above the base, 

 and near the middle. 



The exserted portion of the fang, or that which extends 

 the cone of the crown, is from nine to ten lines high, and 

 seventeen lines in diameter at base. The inserted portion is cylindrical, three 

 inches in length, and rounded at the bottom. It was coossified with its alveolus, 

 as indicated by firmly attached portions of bone to its inner side. Its canal of 

 communication with the pulp cavity of the tooth is completely occupied by a coarser 

 ossific substance. On the inner side posteriorly there exists an excavation, one inch 

 and a half deep and three-quarters of an inch wide, being part of the cavity for a 

 successional tooth. 



4. A tooth, from the Green-sand of Freehold, Monmouth County, New Jersey, 

 belonging to Dr. C. Thompson, and loaned to me for examination through Prof. 

 Cook. It is represented in Fig. 1, Plate X, and is rather larger than the preceding 

 specimen, which it resembles in form. 



The enamelled crown, broken at the apex, when perfect measured about two 

 inches and a half in length; its diameter at base antero-posteriorly is fourteen 

 lines, transversely fourteen lines and a half. The outer and inner surfaces are 

 defined by well-marked acute ridges, which are minutely denticulated. The outer 

 surface is an inch wide at the bottom of the crown, three-fourths of an inch at its 

 middle, and is subdivided into three planes. The inner surface forms more than 

 half a circle, whose radius is about seven lines, and it is dis- 

 tinctly subdivided into eleven planes. The circumference of 

 the crown at the enamel border is four inches, to which the 

 inner surface contributes two inches ten lines ; the outer sur- 

 face fourteen lines. The accompanying outlines. No. 2, 

 represent sections at the base of the crown, and from the 

 lower and upper third. 



The fang is three inches and three-fourths in length, and 

 appears not to have been coossified with its alveolus ; at least 

 it exhibits no traces of attached portions of the jaw. The bottom of the fang pre- 

 sents a wide elliptical pit, narrowing into a fissure, continuous with the canal of 

 communication with the pulp cavity of the tooth. The inner side of the fang 

 posteriorly presents an excavation (Fig. 1, d) for a successional tooth, and a second 

 (c), shallower impression, to accommodate a successor to the functional tooth in 

 advance. 



5. The shed crown of a tooth, from near Woodbury, Gloucester County, New 



