xX THE CHICAGO ACADEMY OF SCIENCES. 
The bibliography includes every reference to the species under 
discussion, which the writer has been able to secure. When the 
species has been cited erroneously under another name, that fact is 
stated, if known. The descriptions of the shells have been made as 
full as possible; it will be noted that the measurements of the spire 
includes that portion of the shell from aperture to apex, in this re- 
spect differing from those of many writers, who included in the spire 
all but the body whorl. Measurements are given of several speci- 
mens from different localities. It is believed that the location, number, 
and catalog entries of the types will prove of value to future students 
of the family. The same is true of the type locality which is given 
in each case. With few exceptions, the types of all American Lymnzas 
have been seen and examined. The descriptions of the anatomical 
features have been made with great care; each drawing represents the 
combined examinations of many different individuals in order to check 
the results. No great difference was found in the genitalia at dif- 
ferent seasons of the year. The organs, when at rest, appeared the 
same in the breeding as in other seasons. The figures of the radulz 
have been made with exceptional care as the cusps are difficult to see 
and errors are easily made. . 
The distribution maps, both recent and fossil, are arranged by 
means of symbols to show at a glance the range of the species in the 
different river systems. The large symbols represent actual records 
while the small dots indicate the probable range of the species. Records 
outside these areas are to be viewed with suspicion until verified by 
competent malacologists. The list of records is arranged alphabetically 
by states and will doubtless be found of use to those malacologists 
who may be working up state lists. In a few cases (palustris, stag- 
nalis, etc.) it has not seemed necessary to include these records, as the 
species are universally distributed over a large area. Under ecology 
is given all available information concerning the habitat relations of 
the species. This is a subject which has received scant attention and 
there is a wide field for excellent work in this direction. Large col- 
lections should be made from restricted areas and exact notes on 
habitat relations as well as photographs should be secured. Much light 
will be thrown on the exact relationship of several obscure species by 
studies of this kind. Under remarks considerable information is 
given concerning the species as well as comparative notes indicating 
the specific or varietal differences. The figures on the plates illustrate 
the species as it appears in different localities and at different ages. 
They also indicate something of the range of variation. 
