356 THE CHICAGO ACADEMY OF SCIENCES. 



Length. 



Breadth. 



Ap< 



;rture length. 



Breadth. 



28.50 



12.00 





14.00 



6.50 mm. 



32.00 



11.50 





14.00 



6.00 " 



30.50 



13.50 





13.25 



7.50 " 



27.50 



11.50 





12.50 



6.00 " 



29.00 



11.25 





13.00 



6.00 " 



25.50 



10.00 





11.50 



6.00 " 



23.00 



9.00 





9.50 



4.75 " 



20.00 



10.00 





10.50 



5.50 " 



Types : Chicago Academy of Sciences, two specimens, No. 23622 ; 

 cotypes, five specimens, No. 23624; coll. L. E. Daniels; Academy of 

 Natural Sciences of Philadelphia ; Smithsonian Institution ; State 

 Museum, Indianapolis. 



Type Locality : Lake Maxinkuckee, Indiana. 



Animal : Resembling rcflexa in form ; color ranging from horn 

 color to jet black; usually light yellowish flecked with white all over. 



Jaw : Superior jaw wider than high, much arched, the inferior 

 margin with a strong, acute median projection; the anterior angles of 

 the lower margin form two triangular projections. The jaw is in all 

 respects like that of palustris ( See PI. VI, fig. 1 ) . 



Radula : ( PI. IX, figs., B.C.) Formula : jL\ + ¥ i T + 1 + \ + | 

 + ^i T -f gl_\ (28-1-28) ; central tooth as in reflexa; lateral teeth 

 bicuspid, the mesocone very large, acute, the ectocone small and wide ; 

 intermediate teeth tricuspid, the entocone small and placed near the 

 lower end of the mesocone ; the eleventh tooth has the entocone and 

 mesocone of equal length ; marginals long and narrow, claw-shaped, 

 the distal end with from three to five denticles of variable length ; the 

 first four or five marginals have one or two small cusps on the outer 

 margin. In one membrane the tenth tooth (first intermediate) had a 

 swelling in place of an entocone (pi. IX, fig. C). 



The transition from lateral to marginal teeth is very abrupt in 

 danielsi, and the marginal teeth are very variable in the form and num- 

 ber of the denticles. There are about 110 rows of teeth. 



Genitalia: (PI. XIII, fig. C) Male Organs: Penis short and 

 thick, 2.50 mill, long, with a rounded head; penis-sac large, 3.50 mill, 

 in length; penis retractor (3.00 mill, long) and penis-sac retractor (2.00 

 mill, long) flat, the latter inserted in penis-sac by about five small 

 branches ; protractor muscles seven in number, four posterior and 

 three anterior, each bifurcated as it joins the penis-sac; vas deferens 

 18.00 to 20.00 mill, long, rather thick; prostate duct about 6.00 mill, 

 in length, slightly enlarging as it enters the prostate; prostate very 

 large, flattened, elongated, squarely rounded proximally and gradually 



