1936] Halt, Hyraxes Collected by American Museum Congo Expedition 125 



Separation of Malar and Lacrymal Bones 



The malar and lacrymal bones of Procavia j. lopesi usually come in 

 contact before Stage VIII. In only one of ten Stage VIII skulls is there 

 any separation, and this is but slight. Two Stage VII skulls have a gap 

 of about 1 mm. between the bones, while two in Stage VI already have 

 the bones in union. Three Stage V skulls show a gap between the two, 

 while two in Stage IV show it closed. In three Stage III skulls there is 

 contact of malar and lacrymal, while in a fourth these bones are sepa- 

 rate. Thus for the rock hyrax of the Upper Uele it seems the rule that 

 there is union of these bones in adults, but that the time of first contact 

 is exceedingly irregular and may occur very early in life. 



Union of malar and lacrymal bones in the Congo tree hyrax is rare, 

 having been observed in only one of 24 Stage VIII skulls and in none of 

 the nine skulls of earlier stages. It is further evident from an examina- 

 tion of the table of cranial measurements of Stage VIII specimens that 

 the distance between these bones is on the whole fairly constant in the 

 species. 



These observations bear out Brauer 's (1934) conclusion that the 

 malar-lacrymal relationship serves as a good generic character. 



The Breadth of the Lacrymal Process 



Brauer has used the breadth of the lacrymal process in characteriz- 

 ing species, but the great individuality shown in the size of this process 

 among series of hyraxes from a single locality suggests that this is in- 

 significant and useless as a criterion. In Stage VIII Procavia j. lopesi 

 this process varied from 2.2 to 3.3 mm. in width, while in Dendrohyrax d. 

 emini the range is from 2.5 to 5.5 mm. This variation embraces the 

 width of practically any specimen of hyrax in the Museum's collection, 

 and the character is not believed to be of use in so far as the species here 

 represented are concerned. 



Position of Lacrymal Foramen 



The position of the lacrymal foramen was found by Brauer to be of 

 significance in some cases. In the Congo collection there is high vari- 

 ability in this structure that is uncorrelated with either age or sex, and 

 though this variation is far greater in Dendrohyrax d. emini than in 

 Procavia j. lopesi it is believed that the feature cannot at present be 

 considered stable in either species and hence reliable for taxonomic 



