THE NATURAL HISTORY SURVEY. 259 
Subfamily Limnzinz. 
“Lateral jaws present. Rhachidian tooth simply pointed: 
laterals provided with numerous denticles. Tentacles flat- 
tened. Genitalia on right side.” (Dall.)+ 
Genus LIMN4AEA Lamarck. 
Shell: Spiral, generally thin, corneous, ovately-oblong or 
elongate; spire long, sharp; aperture oval, generally small; 
columella with an oblique plait across the middle. 
Animal: With short, wide, rounded foot; head support- 
ing a vela area; front edge of mantle much thickened, simple, 
not projecting beyond the plane of the aperture; tentacles 
much flattened, triangular, the eyes sessile upon the inner 
bases; other characters as in the subfamily (Pl. xxxiii, Figs. A, 
B, C); ova deposited in a jelly-like mass without apparent en- 
velope. 
Distribution: World-wide, but preferring temperate re- 
gions. 
KEY TO SPECIES OF LIMNZA.* 
A. Shell 50 to 60 mill. in length. 
a. Aperture and spire about equal in length, the former 
MIC ER AMMEN. Corea hake oe ed dhe wate ge won snack stagnalis 
B. Shell 20 to 40 mill. in length. 
a. Spire attenuated, longer than aperture, the latter 
strongly reflexed; surface very rarely malleated......... reflexa 
: b. Spireand aperture about equal in length; surface nearly 
always heavily malleated; shell wider in proportion to 
length than (a)...................4. RA rec palustris 
C. Shell 15 mill. or less in length. 
1. Surface distinctly striated, with coarse, raised, spiral 
ULIRGS eptes rer terereh eater stare cles Be ater iaioneate Tonto telat na lalcieeerete en's caperata 
2. Surface with fine, impressed spiral lines. 
a. Spire equal to aperture, shell fusiform............ catascopium 
c. Spire one-third to one-half the length of the aperture. 
{Spire sharply conic, aperture two-thirds of length 
SMa ctor aires toc oleh etetioter trriags Ca aareticn Rive arate y ecayacse ale 6s columella 
+tSpire depressed conic, aperture three-fourths of 
MSIE EM ea tl ae He A oa cig MLZ Nog Goel cite ee wrest Bako ood) avd woodrufi 
d. Spire two-thirds the length of the shell, whichis sca- 
PAN UE CUS YTPeM aot inate re eit a ctr late aie xie’anus eo havefel kccvo/laye; owl’ a's Serrisst 
3. Surface without spiral lines. 
a. Spire short conic, aperture roundly ovate, not pro- 
GUGEM AE LECMOWEL DATE. sadn ci i vole cecuss ce egne en humilis 
b. Spire long and pointed, aperture long-ovate, pro- 
MIUCHU AL AHEAOWOF PATEG v4 40 orcis cts dv ake t pales slows» desidiosa 
+Ann. and Lyc. Nat. Hist., Vol. IX, p. 348, et sec. All quotations of Dr. Dall are from 
this work. 
*The account of the genus Limnaa is a modification of the author’s paper in Trans 
Acad. Sci., St. Louis, VoL. IX, No. 1, 1901. 
