RACCOONS OF NORTH AND MIDDLE AMERICA 19 



bones of the skull become coalesced, among the last to unite firmly 

 behig the nasals and the mandibles. A well-developed, sometimes 

 high and trenchant, sagittal crest commonly present in the older males 

 is less freciuent and less prominent in the females; but in many old 

 ackdts of both sexes the temporal impressions do not unite to form a 

 crest. The deciduous dentition is retained only a short time. The 

 l)ermanent middle incisors appear before the molars. 



In the continental forms of the subgenus Procyon subspecific dis- 

 tinctions rest upon combinations of relatively slight characters, 

 indicating close relationships. Although the characters do not stand 

 out very conspicuously as a rule, and due allowance must be made for 

 individual variation, they are maintained with a fair degree of con- 

 stancy over areas often of considerable extent. Some of the more 

 extreme forms of the intergrading series are very similar in external 

 appearance, but are differentiated by well-marked details of cranial 

 structure. Skull characters, rather than color, must therefore be 

 relied upon in determining systematic relationships. In dental 

 sculpture all the forms are very similar, but they vary greatly in the 

 size of the teeth and, to some extent, in the form of the molar crowns. 



In tracing the relationships of the numerous forms of the subgenus 

 Procyon the principal characters of taxonomic value are the following: 

 General color, whether light or dark, plain grayish, or suffused with 

 ochraceous l)uft", or varying shades of rusty rufous; relative develop- 

 ment of the black mask, whether continuous across middle of face, 

 extent of black postauricular spots, and of white facial markings; 

 general form of the skull (especially of the brain case and the frontal 

 profile), massiveness, development of postorbital processes and of 

 zygomata, width of palate, size of auditory bullae; size and relative 

 length and breadth of large molariform teeth. The males are usually 

 decidedly larger than the females in all dimensions, but the sexes agree 

 closely in details of cranial struct ui'e. 



pela(;k and molt 



The pelage differs widely in the subgenera Procyon and Euprocyon, 

 as pointed out in the treatment of subgeneric characters. In the 

 subgenus Procyon it is longer, softer, and much denser than in Eupro- 

 cyon, the denseness being largely due to the fine underfur, which 

 differs in texture from the longer overfur or guard hairs, and which is 

 absent in Euprocyon. Owing to the differences in density and texture 

 of the hairs, Euprocyon is of little value for the fur. 



The annual molt in the subgenus Procyon extends over a lengthy 

 period (kn-ing the summer, at least in the more northern and more 

 lieavily furred subspecies. The new pelage, rather short in the falL 



