118 ntOCEEDINGS OF THE NATIONAL MUSEUM. 



been somewhat difficult to determine the line of union. On the left 

 side there is, at a distance of 32 mm. from the midline and at the 

 anterior border of the frontal bone, a small foramen from which an 

 indistinct, irregular line may be traced for a few millimeters for- 

 ward. This line is shown on plate 7, figure 1. At the corresponding 

 position on the left side of the figure is seen a white line. The bone 

 on the right of this line had been separated and later cemented on 

 again. On close examination it is found that there are here well- 

 defined sutural surfaces, the maxilla joining the outer border of the 

 nasal. At this point the distance from the outer edge of one nasal 

 to that of the other is 57 mm. To what extent the naso-maxillary 

 sutures determined the lines of fracture seen on the upper surface 

 of the snout is uncertain. 



The lachrymal is articulated principally with the maxilla, but its 

 upper hinder border joins the frontal; while below it is united with 

 the anterior end of the malar. It shows a large lachrymal foramen 

 well in front of the orbit. This foramen is the outer opening of a 

 canal which followed inward soon turns and is directed forward, 

 opening into the nasal chamber just in front of the upper end of the 

 first tooth. 



In viewing the skull from below (pi. 7, fig. 2) there are observed 

 behind the ear opening the small condyloid foramen and the large 

 foramen lacerum posterius. The ear opening has a diameter of 10 

 mm. On the right side the tympanic bone is in its place, forming a 

 ring which is incomplete above. Below it is inflated into a bulla of 

 moderate size whose external surface is rough. On the left side the 

 tympanic is missing, a fact which shows that it had not become 

 ankylosed to the contiguous bones. The absence of the bone permits 

 a view of a part of the petrosal. In front of the petrosal is seen 

 the foramen lacerum medius. This, as it appears, is divided into 

 two parts, the more anterior and outer being well in front of the 

 external auditory meatus. 



In front of the great pterygoid bulla is seen the foramen ovale. 

 On the right side there is, in front of the ovale, an opening, the 

 sphenoidal fissure. On the right side there are here two foramina, 

 the hinder of which is probably the foramen rotundum. Farther 

 in front and somewhat higher up and nearer the midline are the 

 canals for the optic nerves. It is evident that these opened out at 

 points in advance of the middle of the length of the skull. 



A feature which distinguishes this genus from other Gravigrada 

 is the presence of the great pterygoid bulla? (pi. 7, fig. 2). As shown 

 in Reinhardt's figures of N. es'cnvanense these inflations extend well 

 below the midline of the base of the skull. They have their lower 

 surface divided by a longitudinal furrow, broad and deep, into an 

 external portion and an internal. In the specimen from Texas the 



