LYMN^ID^E OF NORTH AMERICA. 169 



vidual (3) the posterior retractor was entirely separated from the 

 anterior, the penis retractor being inserted at both ends; in another 

 specimen (plate X, B) the penis retractor was entirely separated from 

 the posterior penis-sac retractor, with many fine muscles connecting 

 with the penis-sac. 



TABLE OF MEASUREMENTS. 



Locality. 

 Rochester, N. Y. 



La Porte, Ind. 



Dissection No. 23066; Shells Nos. 23078, 23079, 23059. 



The characteristic features of the genitalia of columella are the 

 cylindrical form of the prostate, the larger size of the penis, the number 

 of the penis-sac retractors and the insertion of the penis retractors 

 on the posterior penis-sac retractor. 



RANGE: (Figure 12) Nova Scotia west to Minnesota, eastern 

 Kansas and central Texas; Manitoba and Quebec (N. Lat. 52) south 

 to Texas and Florida (N. Lat. 27). 



The records show that columella has a wide range throughout the 

 eastern part of the United States. It does not occur in the great plains, 

 its western extension seeming to be bounded by the edge of the prairie 

 region of the Mississippi Valley (about longitude 100). It is also 

 absent (apparently) from the Appalachian Mountains. It is not a 

 typical species of the great lakes, its center of distribution being at 

 about the 40th parallel. Additional records are needed to establish 

 its northern as well as its extreme southern range. Comparing the 

 distribution with the regional map, we find that columella is found in 

 the Canadian, Upper and Lower Mississippian, Nova Scotian, Caro- 

 linian, and Rio Grandian regions. A single record from the Hudsonian 

 region and one from Lake Superior (Dall) show that the species has 

 a considerable range in this region. The records indicate that a rather 

 wide area between northern Minnesota and Wisconsin, and Manitoba 

 (Lake Winnipeg 1 ), is badly in need of exploration. There is perhaps 

 little reason for doubting the Manitoba records, but it would be very 

 reassuring to have them confirmed by additional collections from this 

 and adjacent territory. 



Columella occupies the drainage areas of two great river systems, 

 the Mississippi and the St. Lawrence, as well as the various streams 



*No exact locality is given for this record and it is therefore not indi- 

 cated on the distribution map. 



