300 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lu 



River system, and it is to be expected that further explorations will 

 greatly augment the list of forms inhabiting northwestern North 

 America. 



Endemism apparently is characteristic of several species on a ver37- 

 localized basis. Most of the species are known from a number of 

 localities even though the totality of the specific range may be very 

 modest; but several forms are still known only from their type 

 localities. In a general wa}^, it appears that species of moderate 

 size enjoy the widest distributions, with both very large and very 

 small species being more or less limited to relatively small confines — 

 usually in mountainous regions. 



Goodnight (1939), on the basis of tlie 21 species of the family which 

 he knew from North America, established four major faunal assem- 

 blages (he called them "faunal regions") characterized by various 

 groups of species and genera. Now although the recognition of 

 faunal assemblages associated with different physiographic regions 

 is a natural and very desirable outgrowth of sj^stematic studies, it 

 must be obvious to the most naive that such arrangements are no 

 better than the current state of taxonomic knowledge. Goodnight's 

 proposal was made 20 j^ears too soon, at the very least, since he loiew 

 but a fraction of the actual number of American species of Branchi- 

 obdellidae. 



SuBGENERic GROUPINGS. — Generally any large ensemble of species of 

 a given genus will be divisible into groups of related forms, although 

 the actual degree of affinity may be quite variable. Since an under- 

 standing of phylogeny and evolution depends largely upon the 

 arrangement of species into progressiveh' smaller ranks with progres- 

 sively greater interspecific similarity, I have endeavored to allocate 

 the species of Camharincola which I have personally studied into a 

 subgeneric classification. This system is above all a subjective one, 

 both in the selection of diagnostic characters and the relative impor- 

 tance assigned to each. That it will be imnmne to future modifica- 

 tions, or even abolition, now seems improbable. I suggest a basic 

 division into three sections, two of which are large and diverse enough 

 for further refinement into groups. In one case, subgroups are intro- 

 duced. 



Checklist 



Figures 

 Mesochorea section 

 Mesochorea group 



C. ouachiia, new species 8, 9 



C. restans, new species 7, 10 



C. mesochorea, new species 6, 11, 12, 13 



Macrocephala group 



C. macrocephala Goodnight 14-17, 19 



C. holti, new species 18, 20 



