12 
locality may have been in either of these states and counties. Say gives 
the locality as French creek near lake Erie, but some later authors (Dali, 
Alaska Moll., p. 88) give French creek, lake Erie. The creek does not flow 
into lake Erie. Since so many diverse forms have been called trivolms it 
becomes necessary to fix the form to which this name should be given. Say's 
figure in the American Conchology is excellent and is of the size and form 
of the figures on Plate III of this paper. The size of the French Creek 
specimen is said to be three-fourths of an inch in diameter (breadth) and 
specimens from western New York occur abundantly in almost every river 
and creek, and in the small bays that line the shore of lake Ontario, which 
correspond to this size and to Say's description. Four specimens from 
Braddock bay, near Rochester, N.Y., have the following measurements 
(Plate III, figures 1-4). 
H. 9-0: Gr. diam. 20' 5; Ap. H. 8-5; D. 6’5 mm. Univ. 111., Z29789. 
H. 9-5; Gr. diam. 19-5; Ap. H. 9’0; D. 6*0 mm. Univ. 111., Z29789. 
H. 7*5 ; Gr. diam. 18-5; Ap. H. 6’8; D. 6-0 mm. Univ. 111., Z29789. 
H. 9*0; Gr. diam. 19*2; Ap. H. 8*1; D. 6-1 mm. Univ. 111., Z29789. 
These measurements conform closely to Say's original specimens. 
Some specimens from New York and elsewhere measure 25 mm. or more in 
diameter. Helisoma trivolvis has a rather depressed shell axially, is of 4^ 
to 5 whorls, subcarinated above, the first three whorls flattened or even con- 
cave, laid tightly against the enveloping whorl without distinct suture, the 
outer edge of the inner whorls forming a sharp carina at the shoulder; the 
last whorl has a more or less sharp angle in the centre; the base shows three 
full whorls in adult specimens, the inner whorls usually subangulated, 
the last 1^ whorls rounded; in young specimens and on some adult indi- 
viduals there are several spiral ridges; umbilicus small; sculpture of distinct, 
low, crowded riblets (3 to 4 in 1 mm. on body whorl), the spaces several 
times as wide as the riblets ; aperture a trifle higher than wide, either flat or 
slightly rounded below and rather sharply angled above where it is much 
narrowed; the aperture is more or less pyriform in outline; outer lip and 
border of aperture usually but little reflected or expanded, thickened within 
and bordered inside by a brownish band. Say’s types of trivolvis are in 
the Academy of Natural Sciences of Philadelphia. 
This type of shell is abundantly distributed in the northeastern part of 
the United States from Maine westward to Nebraska. The southward ex- 
tension of the typical form appears to be northern Illinois and Indiana, 
Ohio, Pennsylvania, and New Jersey. Distinct races carry the distribution 
southward to Florida, Mississippi, Louisiana, and Texas, including the 
races lentum, pseudolrivolvis, and intertextum. In the Rocky Mountain 
region trivolvis is replaced by other species, several of which extend their 
distribution into Canada. 
The distribution of trivolvis in Canada is not well known, owing to its 
confusion with other species. It is apparently common in Quebec, and 
specimens have been examined from Ottawa river, near Ottawa. Mr. A. 
LaRocque of the National Museum of Canada has examined all the 
material in the National Museum of Canada and also in his own personal 
collection, and states positively that typical trivolvis occurs in the Ottawa 
