18 



Trans. Acad. Sci. of St. Louis. 



aperture length 7.50 

 •' " 12.50 



" '« 14.00 



" " 13.00 



12.50 

 15.00 

 13.50 

 12.00 

 16.00 



width 3.76 mill. 



" 5.50 ** 



" 7.00 •' 



'' 6.00 *' 



^' 5.50 " 



" 8.50 '* 



'< 6.50 '' 



'^ 7.00 '* 



»' 7.50 '^ 



columella oblique, with a heavy plait across its center, run- 

 ning up into the whorl and extending to the apex; the colu- 

 mella callus is heavy, wide and spreading, and, with the 

 columella, is reflected so as to completely cover the umbilicus ; 

 umbilical region indented. 



(8382.) 

 (8384.) 

 (8111.) 

 (8111.) 

 (8109.) 

 (8109.) 

 (8110.) 

 (8110.) 

 (8112.) 



Animal: Bluish-black or black; foot short and wide, 12.50 

 mill, long, 6.50 mill, wide; other characters as in palustris. 



the head is carried but little in ad- 

 vance of the edge of the shell (/. 

 10). 

 Jaws: As usual. 



Radula formula: J^ + f + ^ 

 + i + ^2^ + |-ff1: (40— 1 — 40): 

 central tooth as usual ; lateral teeth 

 with a subquadrate base of attach- 

 ment ; reflection large, a little longer 

 than wide ; bicuspid, the inner cusp 

 very large and sub-bifid, the second 

 part represented only by a swelling 

 on the inner side of the cusp; the 

 outer cusp is short and narrow, and pointed; intermediate lat- 

 erals and marginals tricuspid, the central cusp long, the outer 

 cusps short; as the marginals are approached the reflection 

 becomes narrow and the inner cusp is placed nearer the top 

 of the tooth; marginal teeth long and narrow, of the usual 

 type (/. 11). 



Distribution: Northern United States and Canada, from 

 the Atlantic to the Pacific. 



Geological Distribution : Pleistocene; Loess. 

 Habitat: Found plentifully in creeks, ponds, lakes and 

 rivers, attached to pieces of floating wood, submerged vegeta- 



FiG. 10. Mouth parts of 

 Limnaea rejlexa Say. A, 

 superior jaw; B, lateral 

 jaws; C. radula; D. lips. 



