154 THE CHICAGO ACADEMY OF SCIENCES. 



Lymnaa stagnalis lilliance Baker, Nautilus, XXIII, p. 112, February, 1910. 

 Lymncea stagnalis var. Daniels, Nautilus XXII, p. 120, 1909. 

 Lymnaa stagnalis var. Walker, An. Rep. Mich. Geol. Surv. 1908, p. 289, fig. 

 63, No. 1, 1909. 



Limncea stagnalis Adams, Rep. Geol. Surv. Mich., 1908, pp. 16, 17, 18, 21, 

 1909. 



Shell : Elongate-ovate, with short spire and elongated, narrow 

 aperture, which is typically longer than the spire; whorls flattened, 

 elongated, very flat-sided and sloping, especially the body whorl which 

 is cylindrical; spire sharply accuminated ; whorls o l / 2 to 6; body whorl 

 elongated, flattened, roundly shouldered; aperture long and narrow, 

 slightly expanded; axis strongly gyrate; umbilical region with a very 

 minute, narrow chink; sculpture and nuclear whorls as in stagnalis 

 appressa. 



Length. Breadth. Aperture length. Breadth. 



42.00 22.00 26.00 13.00 mill. 



40.00 19.50 23.50 11.75 " 



39.00 20.00 24.50 11.00 " 



37.50 19.50 23.75 12.00 " 



28.00 13.00 17.50 8.50 " 



Types : Chicago Academy of Sciences, 5 specimens, No. 24554. 



Type locality : Tomahawk Lake, Oneida County, Wisconsin. 



Animal: Similar to that of stagnalis appressa in form; in color 

 varying from yellow to jet black (see ante, page 45 for notes on the 

 animal of this race). 



Jaw : Similar to that of stagnalis appressa. 



R adt'i a • "Formula 16 i 8 ■ is t l ■ 1 5 ■ 8 i 18 



(39-1-39) ; the teeth are similar in form to those of stagnalis ap- 

 pressa; there are but fifteen laterals, in this respect differing from 

 both appressa and sanctcemarice which have respectively nineteen and 

 eighteen laterals; the intermediate teeth are double those of stagnalis 

 and sanctcemarice, and the total number of teeth is less. 



Genitalia : Similar to those of stagnalis appressa ; the penis-sac 

 retractors are two in number, the penis retractor inserted in the pos- 

 terior retractor, as figured on plate XIV, figure A, 2 ; this arrange- 

 ment of the retractor muscles allies this race with appressa rather than 

 with sanctcemarice, in which there is a distinct penis retractor (see 

 plate XIV, figure B). A specimen gave the following measurements 

 (dissection No. 24552) : 



Penis. Penis-sac. Vas. def. Prost. duct. Ret. mus. Rec. sem. Shell. 

 4.00 14.00 47.00 22.00 5.50 9.50 43.50 mill. 



