LYMN^EIOE OF NORTH AMERICA. 437 



TYPE LOCALITY: Sin-yale-a-min Lake, Mission Mountains, west- 

 ern Montana. 



ANIMAL, JAW, RADULA and GENITALIA: Not examined. 



RANGE: Western Montana. A species of the Columbian River 

 drainage (Columbian region) occupying an extension of the Boreal 

 (Canadian) life zone. 



RECORDS. 



MONTANA: McDonald and St. Mary's Lakes, Mission Mountains; Swan 

 Lake and Sin-yale-a-min Lake, Mission Mountains (Elrod). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY: "The most noticeable snail, and the most difficult to 

 secure, was Limnaa emarginata, a small variety. The same species 

 was found very abundantly in McDonald Lake, fifteen miles further 

 to the north, and is also in Swan Lake across the range east. In 

 Sinyaleamin Lake the shells are for the most part singly on stones in 

 the bottom where the water is shallow, or along the bank. They are 

 very light in color and very conspicuous. To secure them it is neces- 

 sary to take a boat, row slowly where the water is shallow, and when 

 one can be seen wait until the water becomes smooth and either pick 

 it off by hand if not too deep, or by some other method. As there is 

 much trouble to determine the depth of the water on such occasions, 

 the task becomes quite difficult, and the result is often a wetting. Our 

 best success was to take an insect net, and with this gently pull the 

 shell off the rock by inserting the net under the snail, thus letting the 

 animal fall into the net. Even this is slow work. The snails have 

 the peculiar habit of letting all holds go when anything touches them, 

 falling to the bottom among the pebbles, where it is very difficult to 

 see them. An entire afternoon was spent fishing for these specimens, 

 a couple of dozen being the number secured, and many getting away. 

 It is readily seen from this that a small bottle may hold the entire 

 catch of an afternoon" (Elrod). 



Collected in McDonald Lake along the, rocks in the middle of the 

 lake and at the outlet among grass and weeds in shallow water. 



REMARKS : Montana may be known by its long spire, obese body 

 zvhorl and rather open umbilicus. The inner lip is turned over more 

 than in emarginata, and the body whorl is more obese and the columel- 

 la smoother than in var. canadensis. It is a very thin shell. The sculp- 

 ture is the most pronounced of any of the American species of Lym- 

 naea. A peculiarity of montana is found in the obese character of the 

 penultimate whorl. 



Montana seems to be entitled to specific rank, presenting a com- 

 bination of characters not connected with emarginata by intermediate 



