10 



Annals of the Carnegie Museum. 



pelage characteristic of 0. jacksoni Thomas (see P. Z. S., 1891, p. 184) 

 from Mt. Elgon. The first, which I designate as 0. helleri is repre- 

 sented by a large specimen from the Chilalo Mountains; the second, 

 0. malkensis, from the village of Malka in Sidamo, by a smaller and 

 slightly darker specimen. To avoid confusion both are described as 

 subspecies of 0. jacksoni. When compared with specimens in the 

 U. S. National Museum, they come nearest in color to 0. orestes 

 Thomas. 



M EASUREMENTS. 



No. 21 c?" No. 29cr '{Vyp^o^ O.Jack- 



( O. helleri), ( O. malkensis), j soni in B.M., 

 Mm. " Mm. Mm. 



Length of head and body 1 175 



Length of tail ! 82 



Length of pes 1 27.5 



Greatest length of skull .... 



Basilar length .... 



Condylo-incisive length .... 



Zygomatic breadth | .... 



Interorbital breadth 4.5 



Length and breadth of nasals 19 X 7.5 



Length of diastema 9.5 



Alveolar length of upper row of teeth . . 11 



Length of palatal foramen 8.5 



Length of mandible .... 



2. Otomys jacksoni helleri subsp. nov. (Plate III, figs. 1-5.) 

 Type from Chilalo Divide Camp, Abyssinia, altitude 9,000 feet, 

 "heath-zone." (Original field-number E. A. M., 7531, Feb. 17, 

 1912.) 



General Characters. — Has the excessively long, soft fur, incisive 

 grooving, and molar lamination of 0. jacksoni Thomas (/. c), but has 

 a larger, more massively built skull, and far greater size of body. The 

 length of head and body of O.j. helleri is 175 mm. as against 120 mm. 

 in the case of 0. jacksoni {ty picas). 



Skull. — The posterior portion of that of the type is unfortunately 

 broken, the molars are worn. Compared with 0. j. malke^isis (see 

 below), 0. helleri is heavier throughout. The greater breadth of the 

 orbital region, the longer and wider nasals, the development of the sub- 

 orbital foramen, the depth of the maxillary region, the size of the 

 molars, and the breadth of the incisors are all particularly noticeable. 

 The dentition of the two forms agrees in that in both the lower incisors 

 have two deep grooves, tlu' ui)per jniir a deep outer and very indis- 



