384 THE CHICAGO ACADEMY OF SCIENCES. 



environs of Philadelphia; intcrtcxta, outlet of Black Lake, Holland, 

 Michigan. 



Animal: Yellowish or blackish, covered with small whitish 

 flecks; foot about as long as the aperture, wide, rounded behind; ten- 

 tacles lighter colored at their tips. 



Jaws: (PI. VI, figs. K., M.) Superior jaw arched, very wide. 

 low; ends acutely rounded; central lobe narrow, acute. 



Radula: (PI. IX, fig. I). Formula: ^ 2 T +3± T +f+i+lH-s±i+ 5 ": 

 (35-1-35); central tooth with a rather long acute cusp; lateral teeth 

 rather narrow, bicuspid, the mesocone very large, spade shaped, the 

 ectocone small and rather wide; the tenth to twelfth (transition) 

 teeth are wide and tricuspid, the entocone splitting off from the meso- 

 cone, and gradually becoming larger; the thirteenth tooth (transition) 

 is very wide, the entocone and mesocone are subequal and very acute ; 

 the true marginals begin at the fourteenth tooth which develops two 

 to three small cusps on the entocone ; outer marginals irregularly -A 

 to 5 cuspid, the cusps being confined to the distal end of the tooth 

 on the extreme outer teeth ; the marginal teeth have one or two small 

 cusps high up on the outer margin. The teeth are crowded on the 

 membrane, fitting more closely than in Galba palustris. There are 

 about 105 rows of teeth. 



Catascopium exhibits some variation in the position of the lateral 

 teeth. Normally the lateral teeth seem to be nine in number, but in 

 one specimen there were ten laterals, in another eleven laterals ; one 

 specimen from the Genesee River, Rochester, X. Y., had a radula 

 with fifteen laterals on the left side and twelve laterals on the right 

 side. Binney (op. cit. p. 55) figures 17 laterals, but this is evidently 

 an error, as no Stagnalis has been seen with so large a number of 

 lateral teeth. 



Genitalia: (PI. XII. fig. B). 



Male organs : Penis slender, usually as long as the penis-sac. 

 which has a much larger diameter than the penis ; vas deferens about 

 twice the length of the penis and penis-sac; penis retractor long (1.50 

 to 3.25 mill.) and slender; penis-sac retractor generally a trifle shorter 

 (1.50 to 2.10 mill.; and thicker than the penis retractor; both re- 

 tractors are inserted at the same point in the columellar muscle; pro- 

 tractor muscles variable in number ; the prostate is very large, flatly 

 cylindrical, narrowing at the posterior end; the duct of the prostate 

 is about half the length of the vas deferens, and enlarges slightly as 

 it enters the prostate. 



