CERCOPITHECUS PETRONELLAE. 1 
NOTE LI. 
ON A PROBABLY NEW SPECIES OF THE GENUS 
CERCOPITHECUS 
BY 
Dr. J. BUTTIKOFER. 
In December 1910 the Zoological Garden of Rotterdam 
obtained, from a dealer, an interesting semi-adult female 
of a Cercopithecus, said to be imported from the Upper 
Congo, and belonging to the Mona-group as defined by 
Mr. R. I. Pocock in Proc. Zool. Soc. 1907, p. 708. 
Cercopithecus petronellae. 
This specimen belongs, as far as I am aware, to a hitherto 
undescribed species, which I propose to name Cercopithecus 
petronellae. 
As it is far from easy to give an exact description of 
a monkey while in life, I postponed it until after its death, 
which took place to day. The description is as follows: 
A narrow, but rather high median crest, beginning near 
INotes from the Leyden Museum, Vol. XXXIV. 
1* 
