336 THE CHICAGO ACADEMY OF SCIENCES. 



the lower inner part of the mesocone slightly excavated, apparently 

 a first indication of splitting to form an entocone. The radula of 

 reflexa is similar to that of palustris, the teeth being, perhaps, a trifle 

 wider. The radula figured in Mollusca of the Chicago Area (p. 279) 

 for reflexa is probably palustris (or elodes), as it corresponds with 

 these species, but not with reflexa, which has a larger number of laterals 

 than palustris. 



GENITALIA (Plate XII, figures A, E) : Male organs: Penis-sac 

 large, cylindrical, 6.00 mill, long and about 1.50 mill wide; penis 3.50 

 mill long, of rather large diameter, muscular, with large rounded head ; 

 vas deferens 24 to 27 mill, long; protractor muscles five to seven in 

 number, three to five slender ones on the posterior face of the penis- 

 sac, and two large, wide muscles on the anterior face; the protractors 

 on the anterior face are made up of about six distinct bands joined 

 together and attached to the penis-sac and to the roof of the body 

 cavity by many branches or insertions; penis retractor muscle long, 

 rounded; penis-sac retractor long, wide, band-like; this muscle be- 

 comes very wide, thin and transparent as it enters the penis-sac; duct 

 of prostate small, 8 to 10 mill, long; prostate large, elongated, wide, 

 gradually narrowing toward the posterior end. 



Female organs : Receptaculum seminis very large, elongate-quad- 

 rate in outline, somewhat constricted in the middle, the duct attached 

 to the large end; duct of receptaculum seminis 8.00 mill. long. The 

 first accessory albuminiparous gland is very large and is ovate in shape. 

 The organs are similar to those of palustris, and are colored as follows : 

 Penis-sac, blackish; prostate, yellowish; receptaculum seminis, purplish- 

 flesh ; the rest of the organs are white or flesh-colored. 



The muscles of the male organ vary widely in form and position. 

 In specimens from Calumet Lake (pi. XV, fig. D), the retractor mus- 

 cles of the penis-sac (2) and penis (3) have each an additional band 

 of muscle; the posterior protractor muscles vary from two to four in 

 number; the anterior protractors are quite uniform, however. The 

 measurements of the various organs gave the following comparative 

 results (dissections Nos. 23600 to 23604, 23538, 23555) : 



Penis- 

 Penis- Penis sac Vas. Prost. Rec. 

 Penis, sac. ret. ret. def. duct. sem. Shell. 



3.00 5.80 4.50 3.25 24.00 10.00 8.50 32.00 Calumet Lake, 111. 



3.50 6.00 4.50 3.50 24.00 10.25 8.00 36.10 



3.50 6.00 4.50 3.50 27.00 10.00 8.00 37.25 " " 



3.50 5.10 5.00 4.00 20.00 9.50 7.25 26.50 Millers, Ind. 



3.50 5.00 3.50 4.75 20.00 8.00 6.00 26.00 



3.50 5.00 3.50 4.00 18.00 8.00 6.00 24.00 " " 



