largest, and the posterior one the smallest : in the upper jaw, as in 

 Mus, the molars present a central row of larger, and two lateral rows 

 of smaller tubercles ; and the molars of the lower jaw have two prin- 

 cipal rows of tubercles ; there are however some slight modifications 

 in the structure of these teeth, which should be noticed. The front 

 molar of the upper jaw has three central tubercles, three smaller ones 

 on the outer side and two on the inner side, and besides these there 

 is a small ninth tubercle on the posterior part of the tooth, which is 

 not observed in the Black and Common Rats ; the second molar has 

 two small extra tubercles, one in front and one behind ; the crown 

 of this tooth therefore presents eight instead of six tubercles, as in 

 Mus proper, and the last molar possesses one extra small tubercle, 

 which is placed on the anterior and outer part of the tooth. The 

 molars of the lower jaw very closely resemble those of Mus decuma- 

 nus. 



In the form of the lower jaw the present animal differs from that 

 last mentioned, chiefly in the greater breadth of the descending ra- 

 mus or angle, which is moreover somewhat raised, and so far ap- 

 proaches the Hamsters. 



The name Cricetomys was proposed for this new subgenus, and 

 that of Gambianus to distinguish the species, and to indicate the lo- 

 cality in which it was first discovered. The principal characters 

 may be thus expressed ; — 



Subgenus ad genera Cricetus et Mus dicta affine, et inter haec me- 

 dium locum tenens. Griceto simile quoad saccos buccales, Muri 

 simile quoad formam corporis et caudse ; hac perlonga et pilis brevibus 

 vestita, inter quos squamae in more annulorum positae videntur. Pe- 

 des ut in Mure. 



Dentes fere ut in Mure. Incisores compress! ; molares radicati, 

 3-3 

 3-3* 



Cricetomys Gambianus. Cri. magnitudine corporis dvplo, vel 

 plus, majore quiim in Mure decumano .- colore fere eodem : auri- 

 bus mediocribus, pilis minutis vestitis ; cuudd corpus cum capite 

 aquante ; pedibus mediocre parvis ; vellere brevi, adpresso, et sub- 

 rigido ; colore cinerescenti-fusco ; pedibus partibusque inferioribus 

 sordide albis ; caudd ad basin, pilis intense fuscis, ad apicem, albis, 

 obsitd. 



unc. lin. 



Longitudo ab apice rostri ad caudse basin 16 



basin auris 2 9 



tarsi digitorumque 2 6 



auris 11 



caudcE 15 



The Gambia Pouched-Rat is about double the size of the common 

 Rat (^Mus decumanus) ; in its colouring and proportions it greatly 

 resembles that animal ; the fur is rather harsher, and more scanty : 

 the general colour of the upper parts of the body is a trifle paler 

 than in Mus decumanus. The head is tolerably long, and pointed ; 



