new Forms of Sciurus, Oxymycterus, &c. 491 



halfway across tlie parietals. Palatal foramina short, widely 

 open, extending backward but little more tlian midway 

 between the premaxillo-maxiliary suture and the front of 

 jA; not leading posteriorly into gutters along the palate. 

 Opening of posterior nares narrow, sliarply V-shaped, its 

 anterior point in front of the hinder edge of ?n^. Bullae small, 

 though longer than in Cherriei, the vacuities in front of 

 them widely open. 



Molars very small, rounded, one or more of them with 

 three laminre only, but this character, at first sight so im- 

 j)ortant, varies within the series. 



Dimensions of the type (measured in the flesh) : — 



Head and body 230 millim. ; tail (lost, of anotlier specimen 

 165) ; hind foot, s. u. 46, c. u. 51 ; ear 23. 



Skull : greatest length 56*5; basilar length 40 ; zygomatic 

 breadth 26-5; nasals 21-5 x 6-7; interorbital breadth 12*2; 

 palate length 18 ; palatal foramina 5*8 x 3*2 ; length of upper 

 tooth series 7*5. 



Hah. Kanuku Mountains, British Guiana. Altitude 

 600 feet. 



Type. Adult male. B.M. no. 1. 6. 4. 112, Collected 6th 

 December, 1900, by Mr. J. J. Quelch, and presented by 

 Mr. F. V. McConnell. 



This is the species assigned provisionally to P. cayennensis 

 in my paper on the mammals from the Kanuku Mountains 

 obtained by ]\[r. Quelch *. The Museum has now received 

 a set of spiny rats from Cayenne, topotypical of P. cayen- 

 nensis, Desm., collected by Messrs Cherrie and Gault, and 

 these show Desmarest^s species to be nearly allied to F. tri- 

 nitatis, with long parallel-sided nasals and large teeth, 

 certainly distinct from the Kanuku animal. 



The variation in the number of the laminae to the pos- 

 terior molars is very remarkable and will need further 

 specimens for its elucidation. One specimen has all three 

 molars trilaminate, the premolar alone being quadrilaminate, 

 another (the type) has the two posterior molars trikaminate, 

 while a third has the last molar alone of this structure. A 

 fourth specimen, indeed, has all the teeth quadrilaminate, as 

 is usual in the allied species, but this example shows certain 

 other differences which make its identity with P. vacillator 

 a little doubtful. 



Dasyprocta lucifer, sp. n. 



A yellow-rumped species allied to D. ruhrata, but larger. 

 Size considerably greater than in D. ruhrata. General 

 * Ann. & Mag. Nat. Hist. (7) viii. p. 152 (1901). 



