272 On some of the Larger Species of Grcomjs. 



expanded anteriorly^ but converging very rapidly posteriorly ; 

 ascending processes of premaxillte surpassing the nasals 

 behind by about a quarter of an inch, the space between their 

 posterior ends, behind the nasals, broader than they are. 

 Interorbital region very mucli contracted, considerably 

 narrower than the muzzle, its edges rounded, neither ridged 

 nor inflated. 



Anterior face of incisors orange-yellow ; their single groove 

 narrow and shallow, less developed than in any other species, 

 its position decidedly inward of the middle line, the inner 

 portion of the tooth being only 43 per cent, of the whole ; 

 front face of the inner portion very faintly flattened as com- 

 pared to the evenly convex outer portion. Molars propor- 

 tionally much smaller than in G. grandis. 



Dimensions of the type skin (B.M. 70. 6. 20. 2) : — 



Head and body 295 millim., tail 95, hind foot without 

 claws 41 *, length of longest front claw (much worn) 15. 



Skull (see below). 

 . Bah. iS. Mexico. Coll. A. Boucard. 



The specimen on which this species is founded is tliat 

 referred to by Mr. Alston f under "Mexico {Qeale; Mus. 

 i?rz^.),and came from the same source and probably the same 

 place as the type of Oryzomys fulgens, Tlios.:|: 



1 have named this handsome animal in honour of Dr. C. Hart 

 Merriam, to whose energy and scientific enthusiasm the recent 

 enormous increase in our knowledge of North- American 

 mammals is mainly due. 



G. Merriami is readily distinguishable from G. mexicanus, 

 of which Dr. Matschie has kindly sent me the original 

 measurements, by its much larger size and by the internal 

 position of its incisor groove. The latter character will also 

 separate Dr. Merriam 's own G. gymnurus, which has, like 

 G. mexicanus^ its " upper incisors with a single median 

 furrow." 



* With claws 47 "5 ; the claws are, however, much worn and, as usual, 

 but little value can be attached to the " with claw " measurement, at least 

 as compared to the far more exact and reliable one -without claws. 

 This latter has not, I believe, been much used in America, but the 

 majority of the Old World zoologists are gradually taking- to it, and no 

 one who has once tried it, and found its simplicity, convenience, and 

 exactitude, would return to the loose and old-fashioned vi&j of including 

 the claws, whicli act as a second variable factor in the most important 

 external measurement that can be given of a mammal. 



t Op. cit. p. 159. 



X Ann. & Mag. Nat. Hist. (6) xi. p. 403. 



