LYMNEIDZ OF NORTH AMERICA. 347 
fiat-sided whorls, the attenuated, steeple-shaped spire, the shallow su- 
tures and the long, narrow aperture. Many specimens have zebra-like 
markings (the form named zebra by Tryon) and in not a few indi- 
viduals the inner lip is erect and causes the whole aperture to stand 
out from the body-whorl. The axis has a distinct twist and some indi- 
viduals have an almost gyrate axis. This fact has led some concholo- 
gists to place it in the genus Acella, The axis is not typically gyrate, 
a fact which may be verified by breaking open the whorls; the species 
is a typical Stagnicola. There is considerable variation in the shape 
of the aperture; in many specimens the twist, so characteristic in re- 
flexa, is entirely absent, while in others, notably in old specimens, the 
twist is markedly developed. The whorls also vary somewhat in ro- 
tundity. 
Lea’s type of exilis is a large shell, with flat-sided whorls and 
with the aperture entire and separated from the body whorl, a patho- 
logic condition frequently seen in the reflexa group. It was collected 
near Cincinnati, Ohio. The figure of exilis in Binney is very poor 
and does not well represent this species. Figures 7 and 9 on plate 
XXXVII are good examples of exilis as shown by Lea’s type specimen. 
There is some variation in the width of the body whorl (1, 2, 7, 8, 
pl. XXXVII), but all have the very flat-sided, oblique whorls and long 
aperture, which will distinguish e-vilis from all related species. Its 
telation to Janceata is indicated in the remarks under that species. 
Tryon’s zebra is a synonym of e-vilis, according to his types and pub- 
lished figures, although he seemed to make it cover any zebra-marked 
shell of the reflexa group, a fact borne out by his remarks in the 
American Journal of Conchology, volume I, page 228, where reference 
is made to Haldeman’s figures of wmbrosa and reflexa, to which the 
true zebra is not especially related. Of Tryon’s type lot of four speci- 
mens, only one corresponds with his figure in the American Journal 
of Conchology, plate 23, figure 4, the others being true evilis. A pe- 
culiar, small form of exilis occurs near Des Moines, Iowa, which is 
small and narrow, with a very heavy varix in the outer lip, showing 
that the animal at some time sustained a long period of estivation. 
The body whorl is very much flattened. This form is frequently iden- 
tified as kirtlandiana Lea. When perfect, e.vilis is one of the most 
graceful and beautiful of the Lymnzas. 
Dr. Dall (Alaska Moll., p. 72) believes that evilis should be 
included in the Acella group with Haldeman’s gracilis (=haldemani). 
While there is a superficial resemblance to haldemani in the flatness 
of the whorls and in the general oblique and elongated shell, an exam- 
