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OPP Abas) ¢ 
THE NATURAL HISTORY SURVEY. 257 
FAMILY LIMNAID/. 
Shell; Varying from long and pointed through oblong- 
ovate and obtuse to discoidal; whorls numerous, varying from 
_ planorboid to sharp pointed; aperture thin, lip simple, sharp. 
Animal; With a wide foot, rounded behind; velar area 
preserved in the adult where they form two side lobes on the 
head; tentacles rather long, triangular or filiform; eyes placed 
on swellings at the inner bases of the tentacles; breathing 
orifice on right side. Mantle prominent. Buccal apparatus 
consisting of one median jaw and usually two or more lateral 
accessory jaws. Radula with either a very small, simple cen- 
tral tooth (Zzmne@a) or a larger bicuspid tooth (Planorbis), and 
numerous lateral and marginal teeth of variable form, being at 
first bi- or tricuspid, then tricuspid, and finally the reflection 
lengthens and narrows, and becomes four or five cuspid, the 
CGT. 
EERE EREE Lara 
apie 
Fig.-81. 
Mouth parts of LIMN#A REFLEXA Say. (Original, from drowned 
specimen.) A, superior jaw; B, lateral jaws; C, radula; D, lips. 
cusps being confined to the extreme distal part of the reflec- 
tion, or serrating the outer edge (Planorbis). . 
The genitalia may be thus described (for L. emarginata var. 
mig helst): 
Male organs: (Pl. xxxiii, Fig. E): As in the Lzmneide gen- 
- erally, the male and female organs are separate (with the ex- 
ception of the hermaphrodite gland) and open by separate 
orifices, that of the male being behind the right tentacle and 
that of the female at the base of the neck near the pulmonary 
opening. The penis sac (PS) is very large, of great length and 
large diameter; it is wide at the exterior opening but narrow 
at the end where the penis is attached. The penis (P) is half as 
long as the penis sac, very long and slender, wifh a rounded 
head, about two-and-a-half times the diameter of the neck of the 
