TYLOTOTRITON. 853 



Femur (figs. 45, 45 a and 45 6) is of moderate length, and rather stout, the head 

 and neck being bent slightly inwards. There is a strong projection on the inner 

 side of the head covered with articular cartilage, which also invests another pointed 

 surface prolonged forwards anteriorly almost on to the neck. At the back of the 

 bone, the former process defines the inner side of a deep pit on the neck, bounded 

 externally by a smaller process. A ridge passes downwards from each process 

 enclosing the notch in a triangular space, the apex of which is downwards and 

 overlooked by a conspicuous process springing from a sharp ridge occupying the 

 upper half of the external margin of the posterior surface of the shaft. Below 

 that point to the condyles, there is a triangular slightly concave surface, with two 

 nutritive canals at its upper extremity. 



The lower end of the bone is a simple transversely elongated articular surface, 

 in contact with the oblique articular surface of the ulna and fibula. A broad but 

 obscure ridge winds spirally round the middle of the shaft. 



The tibia smd fibula do not call for any remark. There are nine tarsal bones 

 (fig. 46) . In the first row the os tarsi tibiale is the smallest and in contact with the 

 inner half of the tibia. The first bone of the second row of tarsal bones is some- 

 what pushed out of position towards the os tarsi tibiale. The metatarsal bones 

 are well developed, and the third and fourth support three phalanges, while the first, 

 second and fifth carry only two each. 



The skull (figs. 21 and 24) is remarkable on account of its short and broad 

 character, associated with depression and great truncation of the posterior portion. 

 It is one-fourth broader than long. It is also distinguished by a pronounced 

 rounded porous osseous ridge running round the upper outlines of the skull arising 

 at the hinder border of the upper process of the temporal, the ridge from either 

 side meeting over the nasals. There is also a short ridge along the mesial suture 

 of the parietals. The fronto-temporal arch is complete and the maxillary touches 

 the quadrate, and the pterygoid is opposed by its anterior maxillary process to the 

 maxilla. The orbit is defined anteriorly by the prefronto -lachrymals and by the 

 vertical plate of the maxilla ; posteriorly by the pterygoid, and superiorly by the 

 head of the squamoso-zygomatic process of the temporal and by the orbital process 

 of the frontal. 



The external nostrils are large rounded orifices lying between the premaxillary, 

 nasal and maxillary. The former bone forms their floor and inner wall; the 

 vertical plate of the maxillary bounds them internally and the nasal roofs them in. 

 The internal nostrils (24) are on a line with the anterior angle of the orbit and 

 are defined by the palato-vomerine, orbito-sphenoid, prefrontal- lachrymal, and 

 maxillary. Their floor is formed by the premaxillary, maxillary, and broad anterior 

 expansion of the palato-vomerine. 



A rather long wide space is left between the nasals superiorly and between the 

 broad plates of the palato-vomerines inferiorly, into which the nasal cartilaginous 

 septum which divides the cavity into two chambers is attached. This openino" 

 which in the dry skull passes vertically through it is defined on the upper surface 



