148 THE CHICAGO ACADEMY OF SCIENCES. 
and measured as follows: Length, 54.00; breadth, 20.50; aperture 
length, 29.50; breadth, 16.00 miil. (No. 70370). The progeny at eight 
months were very narrow, quite unlike the parent shell. _ 
An albino stagnalis is reported by Mr. F. R. Latchford from Chil- 
cotts’ Lake, Masham, Ontario, in the Ottawa Naturalist, VI, p. 118. 
The shell is described as being as ‘‘white as pearl.’ Albinism in this 
species is also reported by several European authors. 
Lymnea stagnalis is the host of several species of cercariz (larvee 
of trematode worms) which infest the pulmonary cavity. They seem 
to occasion no especial inconvenience to the animal.® 
Remarks: A thorough revision and a careful study of a large 
collection of American stagnalis has made it evident that Say’s jugularis 
(as defined by Haldeman and Binney) cannot be separated from 
appressa when large numbers of individuals are examined from various 
localities. When compared singly such forms as figure 9, plate XIX, 
seem quite distinct from jugularis as shown in figure 6, but when 
several hundred specimens are examined from the same locality these 
differences disappear and no line can be drawn between them. Both 
forms occur in the same geographic area and are almost always found 
associated together. They offer no anatomical differences. Say’s types 
of appressa closely resemble Binney’s figure 28, and this form must 
be taken as the type of the race appressa. Haldeman’s figured speci- 
mens of both appressa and jugularis are faithfully portrayed on his 
plates 4 and 5. A specimen of his jugularis measures as follows: 
Length, 44.00; breadth, 21.00; aperture length, 25.50; breadth, 
12.00 mill. 
It is unfortunate that Say’s types of jugularis cannot be found. 
The name was doubtless founded on immature material, as the size 
given by Say is but one inch. Immature individuals of appressa of 
5% or 6 whorls measure about an inch and correspond in every way 
with Say’s description. Say’s reference to a specimen from the West 
Indies is, of course, quite erroneous; the only Lymnza from this region 
resembling stagnalis is Pseudosuccinea francisca, from Cuba, which 
is much smaller and of a different shape. 
Stagnalis appressa 1s a characteristic Lymnea, easily known wher- 
ever found. It differs from typical stagnalis principally in its more 
graceful, fusiform shape. The aperture is more oval and not so angular 
and the columellar callus is more closely appressed to the parietal wall, 
giving the axis a conspicuous twist which is absent in most specimens 
3See Hogg, Trans. Roy. Micr. Sec. III, p. 232, 1870 for description of Cer- 
caria furcata. 

