198 THE CHICAGO ACADEMY OF SCIENCES. 
reeds, but never more than four inches from the base, while A. paral- 
lclus, though rather scare, is found from ten to eighteen inches above 
base. 
“Unlike other Lymnzas, gracilis attaches itself very firmly to its 
resting place. Unless a gentle, sliding movement is made in removing 
it, the delicate lip is apt to become broken in the operation. If traction 
is made along the long axis of the shell, the empty shell will be found 
between thumb and finger, the animal clinging to the reed having suf- 
fered a rupture of its attaching muscle to occur rather than relax its 
hold” (Kirkland). 
“After finding dead specimens of this beautiful species in Belle 
Lake, I was told by Prof. Hubbard that he took ifalive in Heath Lake 
in the previous fall, upon the under side of lily leaves. Later a thor- 
ough search was made for them in the same slécality, but only two 
dead specimens were found. Query,—where do they keep themselves 
in summer?” (Sargent, Minnesota habitat. ) 
In captivity the animal moves about slowly in the aquarium and 
will also rest for hours with half its shell out of the water, the animal 
being attached to the glass side of the aquarium. 
Remarks: Haldemani is the slenderest of our Lymnezas, its 
height beng five times its breadth. It is also very thin and fragile. It 
cannot be mistaken for any other species, its graceful, oblique whorls 
and slender form at once distinguishing it. [From the reports of those 
who have collected this species it would seem to inhabit the deeper 
water generally, coming toward the shore at different seasons. It is 
very common in some localities and rather rare in others. The Lake 
Champlain specimens average rather smaller than the western forms. 
The very appropriate name of gracilis is preoccupied by Ziethen, 
and in 1867 Binney used the name haldemani, as suggested by Des- 
hayes. 

Genus PLEUROLIMNAA Meek, 1866. 
1866. Pleurolimnea MrEK, Check List N. Amer. Fos. Eocene, pp. 9, 34 (type, 
Limnea tenuicostata Meek and Hayden, Eocene). 
1870. Pleurolimnea Dati, Ann. Lyc. Nat. Hist. N. Y., IX, p. 349. 
1876. Pleurolimnea Merk, Rep. U. S. Geol. Surv. Terr., IX, p. 533. 
1883. Pleurolimnea Fiscuer, Man. Conch., p. 506. 
1884. Pleurolimnea Tryon, S. and S. Conchology, III, p. 101. 
1905. Pleurolimnea Dati, Alaska Mollusks, p. 64. 
1908. Pleurolimnea BAKER, Science, N. S., XXVII, p. 943. 
RANGE: Eocene period. 
Suet_: “Differing from the last (Acella) in having small, regu- 
lar surface-coste parallel with the lines of growth, the aperture nar- 
rowed or subangular, instead of rounded anteriorly” (Meek). 
