LYMN2EIDAz OF NORTH AMERICA. OD 
sculpture (see pl. XLIX, fig. H) ; sutures deeply indented; aperture 
very elongate-ovate, somewhat produced anteriorly; peristome thin, 
acute ; inner lip reflected over the umbilical chink to form a thin, narrow 
expansion, which is usually appressed to the umbilical region, giving 
the axis a slight twist; parietal callus very thin; umbilical chink vary- 
ing from distinctly open to scarcely observable; the surface of the 
shell is frequently malleated. 
Length. Breadth. Aperture length. Breadth. Locality. 
9.50 4.50 5.00 2.50 Type of obrussa 
8.00 4.50 4.00 2.00 “ philadelphica 
9.00 5.00 4.50 2.00 os 
15.00 6.00 7.00 210 acuta 
14.00 6.00 6.50 3.00 - 
18.00 Tres) 9.00 Smo re i 
17.00 8.00 10.00 4.00 Haldeman’s figure 14 
19.50 12.50 12.50 7.28 ioe Fj if 
18.25 9.00 10.00 5.00 rh 2 
14.00 6.00 7.15 3.25 Owasco Lake, N. Y. 
13.50 ~ 6.50 7.00 3.50 4 
11.00 5.00 6.00 3.00 Joliet, Ill. 
13.25 7.25 7.25 4.00 * es 
12.00 5.50 6.25 3.20 - 
12.50 6.50 6.50 3.50 Des Moines, Ia. 
11.00 5.00 5.75 3.25 . i 
12.00 6.00 6.00 3.00 Chicago, Ill. 
13.00 5.75 7.50 4.00 . 7 
12.00 7.10 7.00 4.00 Lemont, Ill. 
13.00 6.50 7.00 3.50 5 a 
17.50 8.00 8.50 4.50 Bethlehem, Pa. 
16.00 8.00 9.00 5.00 Lebanon, Pa. 
arene ao 9.00 5.00 . % 
Types: Obrussa Say, two specimens, Acad. Nat. Sci Phil., No. 
58700; philadelphica Lea, Smithsonian Institution, three specimens, 
No. 118687; acuta Lea, three specimens, Smithsonian Institution, Lea 
Coll., No. 118643. 
Type Locaritres: Obrussa, Harrowgate, Philadelphia County, 
Pennsylvania ; pliladelphica, River Schuylkill, near Philadelphia ; acuta, 
pond four miles north of Philadelphia. 
ANIMAL: With a very small, more or less oblong foot, when 
viewed from the base, the anterior and posterior borders rounded ; color 
dark gray or blackish, lighter below, sometimes yellowish, the whole 
surface is dotted with whitish or yellowish, which is specially notice- 
able about the eyes; tentacles triangular, flat, short, more or less trans- 
parent; the black eyes are placed on prominences at the inner base 
of the tentacles; respiratory orifice on the right side, near the angle 
