170 CAENIVOEA. 



reception of tlie crown of the first molar of tlie lower jaw. The first molar is a 

 transversely elongated, antero-posteriorly compressed tooth, with a small external 

 cusp, with two others internal to it at its base, the inner half of the tooth, which is at 

 a still higher level, slightly exceeding in size the external half of the crown, having 

 its free surface concave from without inwards and terminating internally in a rather 

 sharp point. The last molar is also transversely elongated, but very small and only 

 about one-fourth the size of the preceding tooth. It is very simple, being generally 

 bicuspidate, one cusp being external and the other internal. 



The central pair of inferior incisors are the smallest teeth in the lower jaw, and 

 have simple, flattened crowns. The pair external to them are slightly larger and 

 tend to become bitubercular, while the internal pair are considerably larger and 

 have the bitubercular character more pronounced. The canines do not call for 

 remark, and the first premolar is very much laterally compressed and simple. In an 

 example of II . auropunctatus, there are, so to speak, two first premolars on the left 

 side of the jaw, having the appearance as if the tooth had been divided in two. It 

 is not an instance of the presence of the milk and permanent teeth in the jaw at the 

 same time, for it is apparent that they are both newly through the gum. Moreover, 

 the more posterior of the two is considerably longer than the first permanent premo- 

 lar should be, so that it would appear that the posterior of the two is the abnormal 

 tooth. This condition is in no way akin to the observation recorded by Ogilby and 

 accepted by Dr. Gray with regard to the supposed occurrence of two additional teeth 

 in the lower jaw of H. mtticolUs, and which I have explained in another part of this 

 Memoir. The crowns of the first, second, and tliird inferior premolars are triangular, 

 long, and laterally compressed, and at the base of the crown anteriorly, and posteriorly 

 in the first, there is a slight eminence due to a swelling of the cingulum, but on the 

 third premolar a small cusp is developed over the last mentioned of these eminences, 

 both of which are more prominent in it than in its predecessor. In the fourth pre- 

 molar the cusp has become considerably enlarged, and the anterior and posterior 

 processes of the cingulum form prominent ridges. The first molar has the anterior 

 two-thirds of the crown carrying three strong, triangular, divergent cusps, one exter- 

 nal, one anterior, and one internal, the first of these being the largest and longest. 

 The posterior third of the crown is at a much lower level, concave, shelving upwards 

 and outwards, its external margin, in some, showing a tendency to division. The last 

 molar is small, and generally with two anterior and one posterior cusp. But it 

 appears to be the most variable of the teeth, and in S. hrachyurus is quadricuspidate, 

 there being three external and one internal cusp. 



The skull is narrow and elongated, the brain-case equalKng about two-thirds of 

 its entire length, and it is marked anteriorly by a well-defined, post-orbital contrac- 

 tion. The lambdoidal ridge forms a prominent crest truncated above, but with 

 lateral sides, while the sagittal suture is but little elevated, and it is joined immediately 

 behind the post-orbital contraction by the obscure ridges from the tips of the external 

 angular processes of the frontal. The latter processes are very prominent, and are 

 opposed to the inferior, posterior, orbital processes of the maxilla, the tendency being 



