1892.] ON A NEW MONKEY FROM SUMATRA. 613 



fissure) there are numerous counecting furrows ; the whole surface 

 of the brain is indeed divided up by a network of furrows with a 

 development far in excess of anything met with in any other 

 Rodent known to me. The very number and variety in direction 

 and extent of these furrows make it quite easy to select some which 

 can be identified with those upon the cerebral hemispheres of other 

 Rodents. It is of course difficult, if not impossible, to come to any 

 definite opinion as to the significance of the furrows upon this 

 particular brain ; if they are an accidental expression of the possi- 

 bilities of modification in the brain-surface, it is noteworthy that 

 the Rabbit departs very widely from the Simj)licidentati. In the 

 latter group the tendency upon the whole appears to be a stronger 

 development of longitudinal furrows, thus resembling the Ungulata. 



2. On a new Monkey from North-east Sumatra. 

 By E. CoLLETT, C.M.Z.S. 



[Eeceived November 8, 1892.] 

 (Plate XLII.) 



During the years 1888 and 1889, Herr Iversen, one of the pre- 

 parators of the University Zoological Museum of Christiania, resided 

 on the north-east side of Sumatra in order to collect specimens for 

 the museum. 



Through the kindness of two young Norwegians, the Messrs. 

 Kamstrup, who are estabhshed there, one in the district of Langkat, 

 the other in that of Deli, Herr Iversen, by living in turns on their 

 estates, has been enabled to make a very important collection of the 

 vertebrated animals of those districts. As the collection of Ver- 

 tebrates is not yet completed, but is being steadily increased by 

 Messrs. Kamstrup themselves, I intend, at a later opportunity, to 

 give a general account of the whole of the materials furnished from 

 these parts. On the present occasion, however, I wish to give a short 

 diagnosis of a Semnopithecus which does not appear to have been 

 previously described, and to which I have great pleasure in attaching 

 my friend Mr. Oldfield Thomas's name. 



Semnopithecus thomasi, sp. n. (Plate XLII.) 



Diagnosis. — A central occipital crest sloping at first backwards, 

 but rerersed on the occiput ; a lower (indistinct) crest on each side 

 of the forehead. Colour above dark grey, white underneath ; hands 

 and feet black. The cheeks, front, and forehead are white ; a black 

 stripe from the upper jaw to the ear, and a black central stripe on 

 the forehead ; the very old male darker, with the upper part of the 

 head brownish black, front whitish. 



Locality. — Langkat, N.E. Sumatra (7 specimens procured ; Uni- 

 versity Museum, Christiania). 



In form and general appearance this Monkey resembles the group 



