1894.] MAMMALS OF NYASALAKD. 139 



11. Petrodromus tetrad actylus, Pet. 

 a, Ad. sk. <$ . Zomba. 1/6/93. 



12. Pelis serval. 



a, b. 1mm. sks. J $ . Port Johnston. 2/93. 



13. Hyaena crocuta. Erxl. 



a. Ad. c? skin and skull. Zomba. Sept. 15, 1893. 

 The following are the dimensions of the skull : — Basal length 

 233 mm. ; extreme length 286 ; zygomatic breadth 179. 



14. Ehtnchogale l melleri, Gray. 



Rhinogale melleri, Gray, P. Z. S. 1864, p. 575 ; Thomas, P. Z. S. 

 1882, pi. iii. 



a, b. Ad. sks. <3 $ . Eesidency Garden, Zomba. 4/93. 



c. Yg. al. Ditto. 



" Wild fruits are always found inside the stomach of this 

 Mungoose." — A. W. 



The discovery of this fine Mungoose in Nyasaland is of consider- 

 able interest for two reasons. Pirstly,its locality now becomes known 

 with certainty, whereas hitherto it has been only conjectured 2 to 

 occur on the Zambesi, a supposition that now proves to have been 

 well-founded. Secondly and chiefly, owing to the fact that the 

 original, and hitherto unique, specimen presented the remarkable 

 number of five premolars on each side above, further specimens 

 were urgently needed to show whether or not this was the normal 

 number in the species. The importance of this point is exceedingly 

 great, for no other known mammal has more than four premolars, 

 and the exception presented by Rhynchogale has puzzled myself 

 and other writers on the subject 3 . Believing as I do that four is 

 and always has been the maximum number of premolars normally 

 present, at least since middle Mesozoic times, it is something of a 

 relief to find that the one known exception to this rule now dis- 

 appears, as the perfect skull of specimen a 4, has simply the normal 

 number of four premolars, and we may consequently assume that 

 the type was abnormal in its possession of five. 



The occasional abnormal development of five premolars is well 

 known in Carnivores, notably in dogs, and is, I believe, generally 

 due to the fission into two of one or other of the normal set of 

 four. I quite fail to see, as Mr. Bateson would have us do 5 , that 

 such cases are any argument against a belief in the individual 

 homologies of teeth, and are not explainable by the simple process, 

 discovered and described by himself, of the fission of normal teeth. 



1 Nom. nov. = Rhinogale, Gray, P. Z. S. 1864, p. 575; nee Gloger, Handb. 

 Naturg. pp. xxix and 75 (1842). 



2 P. Z. S. 1882, p. 86. 



3 Cf. Phil. Trans, vol. 178, Biol. p. 456, 1887 (footnote). 



4 Specimen b is so old that the teeth are all worn down or broken out, while 

 specimen c is too young to show any teeth at all. 



5 P. Z. S. 1892, pp. 102 et seqq. 



