546 a. Li/cM-Jcer — JYew Sjwcies of Meri/copofamus. 



large size of the canine shows that the mandible belonged to a male ; 

 and the two specimens agree precisely in proportionate size. The 

 symphysis is long and wide, the notch in front of the descending 

 process of the mandible deep, the inner surface of the third lobe of 

 the last lower molar flat, and the crowns of the molars relatively high. 

 The left half of the symphysis of the mandible represented in plate 

 Ixviii. fig. 18 belongs to a female of this form. 



The two crania represented in figs. 3-5 of plate Ixvii. of the same 

 work have considerably shorter jaws and are altogether smaller than 

 the cranium of M. dissimilis ; fig. 3 belongs to a male and fig. 5 to 

 a female individual, as is shown by the size of their canines. The 

 hinder part of the cranium of the female presents a highly arcuated 

 profile,^ in place of the straight one of M. dissimilis. The upper 

 molars of the smaller crania are very similar to those of the latter, 

 but their cusps are somewhat lower. In figs. 7, 8 of the same plate 

 there are figured two mandibular rami which agree precisely in size 

 with the crania above mentioned ; the size of the canine shows that 

 fig. 7 belonged to a female and fig. 8 to a male ; and the following 

 dimensions show the diiference between these specimens and the 

 male mandible of M. dissimilis, viz. : — 



M. dissimilis Small form, 



male. male. female. 



Interval between canine and hinder border of m. 3 0-198 01 63 



Antero -posterior diameter of canine 0-029 0-0295 0-020 



The depth of the three specimens is very nearly the same ; and 

 the third lobe of the last lower molar of the small form is distin- 

 guished by the concavity of its outer surface. The specimen repre- 

 sented (on a larger scale) in fig. 6 of the same plate seems to belong 

 to the smaller form, and shows that the notch in front of the 

 descending plate is less deep than in M. dissimilis. The specimens 

 also show that the symphysis of the smaller form was much 

 narrower and shorter than that of M. dissimilis. 



The foregoing observations clearly show that the differences in 

 size between the two forms are not due to sex ; and this being so, 

 they appear too great to come within the limit of individual variation : 

 this being confirmed by the marked difl"erences in form already 

 mentioned. Under these circumstances there seems no reasonable 

 doubt that there are two species of Merycopotamiis ; and I propose 

 to revive for the small short-jawed form Falconer's MS. name of 

 M. nanus. 



If the necessary sanction be granted, I shall hope on a future oc- 

 casion to refigure some of these specimens in the " Pahieontologia 

 Indica" on a full-sized scale, as the small figures in the "F.A.S." 

 are quite inadequate to exhibit clearly the distinction between the 

 large and the small species. I am at present unable to say to which 

 species the immature cranium from Burma (now in the Indian 

 Museum, Calcutta), figured in plate xv. of vol. i. of the " Palseonto- 



1 The outline restoration of the profile of the two small crania is entirely incorrect ; 

 and was apparently made from the cranium of If. cUtssimiUs. 



