1896.] ;500LOGICAL expedition to MADAGASCAR. 977 



developed in H. Uheriensis, whilst in S. ampJiihius and the 

 H. major of the Upper Pliocene the cranial portion is much 

 reduced, the facial portion on the contrary enormously produced. 

 In connection with this is the great elongation of the frontal bones 

 of H. Uheriensis, whilst they are broad and short in H. ampliibiws 

 and H. major. H. sivalensis is still very near //. liberieiisis in this 

 respect, the antero-posterior extension of the frontal being, as was 

 shown by Falconer and Cautley, twice as great as in H. amphihius. 

 An expression of the relative proportion between the anterior and 

 posterior portions of the cranium is given by the position of the 

 orbits. The various Hippopotamus crania from Madagascar have, 

 in this respect, much resemblance with //. sivalensis, the cranial 

 portion being, however, somewhat more shortened, the facial 

 portion somewhat more lengthened ; so that the orbit occupies a 

 less central position than in -H. Uheriensis, and, as a matter of 

 course, still less so than in H. sivalensis. The Malagasy forms 

 thus constitute a step farther in the direction of II. amphihius, 

 the breadth of the intraorbital region being much less than in the 

 African species and tlie same as in II. sivalensis. 



These changes are reflected by the position which the lachrymal 

 occujjies. In II. Uheriensis, as shown by Leidy, who bad at his 

 disposal the skull of a younger animal, exhibiting distinctly all the 

 sutures, the lachrymal is entirely separated from the nasals by the 

 anterior prolongation of the frontal, which last thus comes in 

 contact with the maxillary. This is, with the exception of the 

 lluminants, almost the rule in Ungulates. As to II. sivalensis, in 

 six out of seven skulls figured in the ' Fauna Antiqua Sivalensis ' 

 the sutures are distinctly to be seen ; and we find here again the 

 lachrymal excluded by the frontal from contact with the nasal and 

 joining the maxillary. The originals of most of the skulls figured 

 being in the National Museum, I have had an opportunity of 

 verifying the accurateness of the drawings, so that we may fairly 

 conclude that H. sivalensis had, as a rule, the character mentioned 

 above in common with //. Uheriensis. The same is the case with 

 regard to //. palwindicus, as shown in the F. A. S., with the slight 

 diSerence that the anterior tongue of the frontal is somewhat 

 shortened. 



In the Malagasy Hippopotami we find, as a rule, the following 

 relations in this part of the skull. The lachrymal departs from 

 the orbital margin in an inward direction and reaches the nasal, 

 with which it unites, thus shutting out the frontal from a connection 

 with the maxillary. Anteriorly to the lachrymal, exactly corre- 

 sponding to the place which in //. Uheriensis and II. sivalensis is 

 occupied by the foremost tongue of the frontal, we find here a 

 separate bone of various dimensions, interposed between the nasal 

 and lachrymal, and touching the maxillary in front and sometimes 

 the malar bone as well. In II. amphihius the lachrymal is usually 

 broadly interposed between the frontal and maxillary ; but in 

 young specimens we meet occasionally with the same supra- 

 numerary bone ; sometimes, as in //. Uheriensis and //. sivalensis, 



63* 



