302 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lu 



segregated into tlii-ee groups based upon more numerous similarities in 

 details of botli body form and reproductive organs. 



Presumably this section includes the more primitive species, or at 

 least those in which presumed primitive characters are preserved. 

 With one exception, each species is remarkably localized, four being 

 known only from the type localities, the fifth from only tw^o places. 

 I should expect that such distributional patterns would be indicative 

 of reliction, following disintegi-ation of a formerly more inclusive 

 range of the parental stock. The localized species now occupy 

 peripheral localities on the known distribution of the section; C. 

 mesochorea alone is widely distributed in the central area. That it is 

 possibly the most specialized of the six correlates well with its present 

 abundance and extensive geographic range. 



Key to Groups of the Mesochorea Section 



1. Prostate gland appreciably broader and longer, in most specimens, than the 



spermiducal gland; latter essentially without distinct lateral deferent lobe. 



Mesochorea group (p. 302) 



Prostate gland equal in size to, or much smaller than, the spermiducal gland; 



latter with either subequal terminally located deferent lobes (thus T- or Y- 



shaped) or with a distinct lateral lobe 2 



2. Spermiducal gland long and cylindrical, terminating in virtually similar 



deferent lobes; prostate fully as long as spermiducal gland. Very large 

 species, with tentaculate peristomium . . Macrocephala group (p. 311) 

 Spermiducal gland shorter, cuneate or acuminate, terminating in a major 

 deferent lobe subtended by a smaller lateral lobe (sometimes these may 

 appear terminal and subequal) ; prostate gland only half as long as spermi- 

 ducal gland or less. Small species, the peristomium not tentaculate. 



Branchiophila group (p. 316) 



MESOCHOREA GROUP 



Proposed for the inclusion of three rather generalized or primitive 

 species, this group is to be ranked at the bottom of the evolutionary 

 scale in the genus, although its components show considerable dif- 

 ferentiation among themselves. Similar in general form of the male 

 sex organs to the species of the Macrocephala group, the present 

 species lack any of the specializations w^hicli mark the others. The 

 prostate is greatly enlarged and the posterior deferent lobe is virtually 

 obliterated in two species although still conspicuous in the other. 



Camharincola mesochorea is fairly widespread over the interior of the 

 continent; C. ouachita is Ivnown only from the type locality in south- 

 eastern Kansas. Tliis is a most unusual relationship and one warrant- 

 ing further study. The two species are very similar in their medium 

 size, general body outhne, jaw structure, and reproductive systems. 

 C. restans is remarkably different from anything else in the genus 

 because of its head size and body shape. The sex organs are much 



