632 PROF. H. G. SEELET ON THE OEANIAL CHARACTERS OP 



in its middle part. The anterior median process has large longi- 

 tudinal cells ; the posterior part has the cell-matter arranged ver- 

 tically. The distance from the basioccipital margin to the median 

 anterior process of the basisphenoid, where the excavation occurs 

 which descends into the bone, is less than 5 centimetres ; and the 

 depth of this process, which is rounded in front, is 17 millimetres. 

 The roof-bones of the skull are marked by the large longitudinal 

 cells, except where the dense substance of the otic bones extends 

 inward, and where the cells are directed obliquely downward and 

 forward at the junction of the supraoccipital bone with the parietal. 



The occipital aspect of the skull appears to have conformed to 

 the usual Teleosaurian pattern, but is too imperfectly preserved for 

 description. The exoccipital bones (Eo) entered into the upper and 

 outer parts of the occipital condyle, and are divided from the basi- 

 occipital, on the articular surface, by a deep suture, which, after 

 leaving that surface, becomes prolonged downward and outward after 

 the manner of existing Crocodiles. The occipita] region appears to 

 have been nearly vertical. The exoccipital bones were laterally ex- 

 panded, much as in living Crocodiles, but more prolonged outward, 

 below the foramen magnum, descending to a level with the base of the 

 occipital condyle. About I5 centimetre from the foramen magnum 

 laterally is a round perforation for the vagus nerve ( Va) ; and below 

 this, and further outward, 3| centimetres from the foramen magnum, 

 is a larger perforation like that in the Crocodile. The exoccipital is 

 fractured vertically at about 6| centimetres from the middle line 

 of the skull. I cannot say whether the opisthotic or paroccipital 

 is distinct; if so, it is very large and makes the hinder wall of 

 the great air-cell. The arrangement of the roof-bones of the skull 

 conforms entirely to the usual Teleosaurian pattern. 



The skull becomes greatly expanded transversely at its hinder part 

 (fig. 4), chiefly owing to the excavation of the large tympanic air- 

 chamber which penetrates the bones; and anteriorly the skull is 

 constricted, so that its least measurement from side to side is about 

 6 J centimetres at this distance from the anterior fracture. The 

 skull then widens out again, so that at the anterior fracture its 

 width must have been about 10 centimetres (fig. 4). Seen from the 

 side, a rounded median ridge (fig. 3), which becomes sharpened in 

 front and which is necessarily concave from front to back, divides 

 the lateral region of the brain-case into superior and inferior aspects. 

 The superior aspect slopes obliquely downward from the median longi- 

 tudinal crest. Its upper part throughout the length of the specimen 

 is occupied by the parietal bone (fig. 4, P). This is fully 4 centimetres 

 deep in front, becomes reduced to less than half that depth in the 

 middle (fig. 3, P), where the skull is most constricted from side to 

 side, and again widens somewhat as it runs backward, and curves 

 outward in a T-shape in the transverse line of the occipital crest. 

 Its outward extension is a thin plate, resting upon a large expanded 

 bone which forms the posterior half of the wall of the brain-case 

 below the parietal. This bone forms the upper part of the wall 



