LYMNjEID^E OF NORTH AMERICA. 305 



tution, three specimens, No. 118649 ; haydeni Lea, Smithsonian Insti- 

 tution, two specimens (one figured type), No. 121505 ; sufflatus Calkins, 

 Chicago Academy of Sciences, two specimens (one figured specimen), 

 No. 8375; plebeia Gould, location, if any, not ascertained; sordidus 

 Krister and septentrionalis Clessin, location not ascertained. 



Type Localities : Expansa, Vermont ; nuttalliana, Oregon ; hay- 

 deni, Yellowstone River ; sufflatus, Chicago, Illinois ; plebeia, Massa- 

 chusetts; septentrionalis, North America; sordidus, unknown. 



Animal : Black, lighter below, the body spotted with white which 

 shows through the shell ; foot wide and short, rounded before and 

 behind ; tentacles short and rather wide. 



Jaw (Plate VI, fig. I) : Wide and rather high, with a rounded 

 median swelling on the ventral margin about one-third the diameter 

 of the jaw in width. 



Radula (Plate VIII, fig. F) : Formula : ^V+f+f+i+f+f+^V 

 (34-1-34) ; central tooth with a rather long, sharp cusp; lateral teeth 

 (9) narrow, bicuspid, the mesocone long and narrow, the ectocone 

 short, rather wide and placed high up on the reflection ; transition 

 teeth (10-13) narrow, tricuspid, the mesocone very long and narrow, 

 the entocone very small and placed a little below the middle of the 

 mesocone; the entocone first appears on the tenth tooth and gradually 

 becomes larger until in the fourteenth tooth it is as large as the meso- 

 cone ; marginal teeth long and very narrow, tri-, quadri or penta-cuspid, 

 the cusps at the distal end of unequal size; there are two outer cusps, 

 one placed about midway of the reflection and one, smaller, placed 

 some distance above this ; the marginals gradually become smaller to- 

 ward the edge of the membrane, and the distal end of the reflections 

 become serrated by three or four cusps of equal size. In one mem- 

 brane examined, the first lateral to the right of the central tooth had 

 a bifid ectocone. This was observed on all the first laterals in this 

 membrane. (PI. VIII, fig. H.) There are one hundred rows of teeth. 



In specimens of palustris from Colorado, the transition teeth be- 

 gan at the ninth tooth, while radulse from California specimens gave 

 the same result as those from Illinois and New York. 



Crosse and Fischer have referred to the lateral teeth of palustris 

 as being tricuspid, but in a large number of examinations of American 

 specimens, from many parts of the country, all have been bicuspid. 

 (See Mis. Scient. Mex., II, p. 41, 1870.) All of the palustris-emar- 

 ginata-catascopium groups have bicuspid lateral teeth. 



Genitalia (Plate XI, fig. E) : Male organs: Penis-sac cylin- 

 drical, 4.50 mill, long, 1.50 mill, greatest diameter ; penis 3.00 mill, long, 



