Dr. J. E. Gray on the species of the genus Manatus. 313 



and breadth of the nasal opening, the extent of the bending down 

 of the front of the upper jaw, the completeness and incompleteness 

 of the orbit, and in the smoothness, roundness, or angularity and 

 rugosity of the gonyx of the lower jaw ; but I think that all these 

 differences may be referable to the age and sex of the specimens, the 

 upper jaw being more deflexed and lengthened as the animal in- 

 creases in age. All the older specimens have a small, conical, ru- 

 gose, bony prominence in the middle line of the front of the lower 

 jaw, and the apex of the coronoid process truncated and expanded 

 into an angle behind and before, as represented in De Blainville and 

 Cuvier's figures of M. australis and M. latirostris. This is even 

 the case in the skull of a very young animal with only the milk teeth. 



On the other hand, in Dr. Baikie's skull of M. Vogelii, and in 

 M. De Blainville' s figure of M. SenegalensiSi the coronoid process 

 of the lower jaw is narrow above, with the hinder upper part ob- 

 liquely rounded off, and with a shght angle in front ; so that this is 

 probably the character of the African species. I may also remark, 

 that the front of the lower jaw of Dr. Baikie's specimen is produced 

 and very differently shaped from that of any of the American skulls, 

 and in this character it differs from M. De Blainville' s figure of M . 

 Senegalensis ; but this difference may be only in consequence of its 

 youth. 



Dr. Harlan observes : — " Cuvier estimates the teeth at 36, nine 

 on each side ; in both my specimens they do not exceed 32, eight on 

 each side.'* 



In the very young skull above mentioned, which has holes for the 

 rudimentary upper cutting or canine teeth, there are only 24, viz. 

 six on each side ; and the two hinder on each side must have been 

 hidden in the gums. In the older skulls some have eight and others 

 nine on each side, but in most of them only six on each side are 

 perfect ; as the anterior one on each side drops out as the new ones 

 are formed behind, and in each of the skulls two hinder on each 

 side are in process of development. 



But the question of the permanent specific difference between the 

 M. australis from Cayenne, the M. latirostris from East Florida, 

 Jamaica and Cuba, and between M. Senegalensis of Blainville (not 

 of Cuvier, which is like the first) and M. Vogelii, must wait for 

 solution until a larger series of skulls of these species can be pro- 

 cured, and until the other parts of the skeleton can be compared ; 

 it being always borne in mind that, at least according to my experi- 

 ence, the skulls and other parts of the skeleton of the animals are 

 quite as liable to vary in form and structure as any of the external 

 soft parts by which they are moulded. 



On the Genus Necturus or Menobranchus, with an 

 Account of its Skull and Teeth. By Dr. John Ed- 

 ward Gray, F.R.S., F.L.S., V.P.Z. &Ent. Soc. etc. 



Dr. Kaup lately sent to me the skull of the Proteus of the Lakes, 

 Necturus maculatus. As it presents some peculiarities, I am in- 



