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PROCEEDINGS OF THE NATIONAL MUSEUM 



condition at maturity or some stage in the sexual activity, some sort 

 of allometric growth, or merely sporadic local variation cannot be 

 established at this time. The situation seems to be restricted to the 

 soutliern Appalachian region. 



There is considerable, apparently geographic, variation in size 

 and shape of the jaws. The attention of future workers is particularly 

 invited to investigation of this matter, something which I have been 

 unable to do satisfactorily. 



As diagnosed and briefly described in the preceding paragraphs, 

 philadelphica ranges from central New York State west as far as 



Figures 39-42.-^Structural details of Camharinccla philadelphica (Leidy). 39, Lateral 

 aspect of typical specimen; 40, jaws of the same specimen, dorsolateral aspect; 41, 

 jaws of another specimen, lateral aspect; 42, reproductive systems, specimen from 

 Frederick Co., Maryland. 



Minnesota, and south through the Appalachians and Piedmont to 

 the Carolinas. An additional form appears to inhabit the Catskill 

 region and adjacent areas, this is generally similar to the typical 

 form but is apparently consistently smaller over a distinct geographic 

 range. At several localities it occurs together with the large phila- 

 delphica. Whether it represents (1) a depauperate northern phase 

 of the main population, (2) a distinct sibling species, or (3) merely 

 an assemblage of young specimens, remains to be worked out by 

 another investigator able to collect and make field studies in New 

 York. 



In central Kentucky and Tennessee occurs a form in which the 

 peristomimn, particularly the dorsal half, is hypertrophied and 

 frequently widely flared, giving the head a campanulate appearance. 

 This is probably a perfectly good subspecies, but the details of its 

 overlap with philadelphica in eastern Kentucky ought to be worked 



