APPENDIX E. 349 

Butte, &. Occurring in very many varictal forms, which are all here in- 
cluded. Specimens from coulée, Traders’ Road measured 36 by43 mm. 
Limnza humilis, Say. Lake of the Woods. Dufferin. Pembina Mountain, Saline 
Lake, E. of Turtle Mountain, Traders’ Road. 
Limnza decollata, Mighels. Lake of the Woods. Abundant on some parts of the 
shores of the Lake of the Woods, generally among rocks and boulders on an 
exposed coast, and creeping over the stones even in the wash of the waves, 
with the habit of a Jittorina. Well grown specimens measure 15 by 11 mm. 
Colour pale, yellowish-brown ; surface marked with lines of growth, which 
are sometimes rather coarse, and in the outer whorl are sometimes crossed 
by gentle, irregular, revolving ridges, dividing the surface into quadrate 
areas, in a manner resembling that frequently seen in Limnza elodes. Well- 
preserved specimens also show very fine and close undulating transverse 
lines, and delicate revolving strie, giving the shell a lustrous surface. Lip 
usually thickened, and tinted brownish-purple. 
Limnza catascopium, Say. Dufferin. Riviere des Lacs. Pool Traders’ Road. Creek 
near East Fork Milk River. West Butte? 
Limneza catascopium. Var pinguis, Say. Creek near E. Fork Milk River. 
Limnza caperata, Say. Dufferin, Pembina Mountain. Pembina River. 
Limnexa pallida? Near Dufferin. 
Physa heterostropha, Say. Lake of the Woods. Pointe du Chéne. Dufferin. 
Physa ancillaria, Say. Lake of the Woods. 
Physa ampullacea, Gould. Creek 13 miles west of Wood Mountain. Measurement 
of largest specimens 22 by 13 mm. 
Bulinus hypnorum, Lin. Lake of the Woods. Pools on Red River prairie. Pembina 
Mountain and River. Turtle Mountain. Riviere des Lacs. Traders’ Road. 
Specimens from Lake of the Woods attain sometimes 20 mm. Those from 
the prairie region reach 23 mm. 
Ancylus parallelus, Hald. Lake of the Woods. 
Ancylus rivularis, Say. Roseau River. Souris River. 
Planorbis trivolvis, Say. Pools on Red River Prairie. Turtle Mountain. Traders’ 
Road. East Fork Milk River. 
Planorbis trivolvis var. macrostomus, Whiteaves. Lake of the Woods. Pools on Red 
River Prairie. 
This variety is not abundant at the Lake of the Woods, but is the common 
form in the pools and coulées of the Red River Prairie, where calcareous 
matter and food equally abound. Some specimens 28 mm. in greatest 
diameter. 
Planorbis campanulatus, Say. Lake of the Woods. 
Planorbis bicarinatus, Say. Lake of the Woods. East Fork Milk River. 
Planorbis corpulentus,Say. Flag Island, Lake of the Woods.—The specimens are 
from Say’s typical locality,and agree perfectly with his description, the form 
being even better marked than in his figure. P. trivolvis, and its variety 
macrostomus, also occur in the Lake of the Woods. If P. corpulentus is also a 
variety of trivolvis, as has been suggested, it is a very well marked one, and 
is characteristic of the open reaches of the lake. 
Planorbis ezacutus, Say. Lake of the Woods. Dufferin. 500 Mile Lake. 
Planorbis parvus, Say. Dufferin. Saline Lake, E. of Turtle Mountain. 
Segmentina armigera, Say. Lake of the Woods. 
Segmentina armigera var campestris, Pointe du Chéne. Dufferin. Traders’ Road. 500 
Mile Lake. Thisis a large fine variety characteristic of the prairie region, 
which I have distinguished by the above varietal name. The normal form, 
with the usual number of whorls (4) is abundant in the Lake of the Woods, 
and surrounding wooded region. Specimens seldom at all exceed 6-5 mm. 
