1905.] ORTMANN— AFFINITIES OF CAMBARUS. 127 
primitive forms of the “mosus-section (aside from C. Zimosus itself) 
are found in Indiana, Kentucky and Missouri, that is to say, in the 
same general region. 
The subgenus 4arfonius has the largest number of species in 
Tennessee (6); then follow: Georgia, North Carolina, Virginia 
and Pennsylvania (with 4 each). The more primitive forms of the 
extraneus-section are found in Georgia, Alabama, Tennessee and 
Kentucky. In Tennessee is also found one of the blind cave forms 
(C. hamulatus). Thus also here is apparently a mutual relation 
between center of origin, location of most primitive forms, and 
center of frequency. ‘This rule, consequently holds good in the 
section of C. d/andingt of the subgenus Caméarus, and in the sub- 
genera Haxonius and Bartonius, while it is not very evident in the 
more primitive forms of the subgenus Caméarus, and in the sub- 
genus Cambarellus.’ 
A few peculiar and striking facts ought to be mentioned especi- 
ally. 
Discontinuity of distribution proof of antiguity.—We have found 
this rule substantiated in the following cases: (1) In the distribu- 
tion of the more primitive forms of the subgenus Caméarus (sec- 
tions of C. digueti and gracilis) ; (2) inthe subgenus Caméarellus ; 
(3) in the “mosus-section of the subgenus Faxonius; (4) in the 
hamulatus-section of the subgenus artonius. The discontinuity 
offered by C. wzegmanni in the alleni-group of the subgenus Cam- 
éarus needs further investigation, and cannot be regarded as estab- 
lished before the systematic position of this species has been posi- 
tively ascertained. 
Morphologically isolated species occupy tsolated stations.—This is 
illustrated by: (1) C. cubensis in Cuba; (2) C. shufeldti in Louisi- 
ana; (3) C. Zmosus on the Atlantic coast plain from New Jersey 
to Virginia; (4) C. harrisont in Missouri; (5) C. alabamensis 
and compressus in northern Alabama: (6) C. sefosws in Missouri 
(cave-form ). 
Closely allied species occupy neighboring areas. —This is most evi- 
1 Addition to our knowledge may change this considerably. I only call atten- 
tion to the fact, that up to very shortly ago only two species of Bartonius were 
known from the state of Pennsylvania. Investigations during the last four years 
have revealed the presence of two more species, thus doubling the number. This 
may happen in any other state. 
