176 NEW YORK STATE MUSEUM 



not sufficient to make hard and fast comparisons, I believe they 

 may be regarded as typical of the area. They are a little over 

 one-half the size of the recent specimens, and are very considerably 

 smaller than the average Montreal shells, which in addition are very 

 much thicker. The largest Montreal specimen measured 37 mm x 

 1 7. 1 mm; average large specimens range from 31 mm x 16 mm 

 to 34 mm x 21 mm; a large proportion of the material shows 

 measurements from 22 mm x 14 mm to 27 mm x 16 mm. The Port 

 Henry material therefore runs about the size of the smaller Montreal 

 specimens, though even the very small specimens from the Montreal 

 area have very heavy shells. {See plate 1, figures 1-5.) 



Localities in the Champlain valley between these two areas show 

 intermediate-sized specimens. At Willsboro the specimens tend to be 

 chunky, short and broad. Only a few are at all large and the majority 

 run rather small. Out of about" three hundred specimens only four 

 of the largest sizes were found and these range from only 25.5 mm x 

 12.8 mm to 28 mm x 13.5 mm. Average large specimens, about 

 ten out of the whole number, vary from 22 mm x 10.8 mm to 23 mm x 

 12.8 mm; but the majority of the specimens measure as follows and 

 smaller: 17.8 mm x 10 mm to 19.5 mm x 11. 6 mm and 20.5 mm x 



1 1.4 mm. At Port Kent, in about the same number of specimens, 

 the shells run slightly larger. The largest sizes, though few in num- 

 ber, are more numerous than in the Port Henry area and range 

 from 25 mm x 12 mm or 13 mm to 29 mm x 14.5 mm. The average 

 large specimens vary from 22 mm x 13.7 mm and 22.6 mm x 11. 6 mm 

 to 23 mm x 12.6 mm and 24.8 mm x 11 mm; but the majority of 

 the shells run smaller: 18.4 mm x 11. 7 mm to 21.7 mm x 11. 6 mm. 

 In this last group belong also shells which run longer, but are much 

 narrower. This variation in the shape of the shells in the same 

 locality will be discussed later. At Valcour island the larger sizes 

 are more abundant and the shells are much heavier again, approaching 

 the condition found in the Montreal area. The species is more 

 abundant here than in any of the other localities and the specimens 

 collected are the largest found in the Champlain valley. The largest 

 specimens range from 28 mm x 17 mm and 29.5 mm x 14 mm to 



34.5 mm x 15.5 mm; the average specimens, and the most abundant, 

 measure 22 mm x 11. 2 mm to 27.8 mm x 14.3 mm and 28 mm x 

 13.5 mm. A large portion of the specimens are under 25 mm in 

 length, varying from 20 mm to 25 mm. In the vicinity of Burlington 

 fragments of a few specimens were found, insufficient for comparison; 

 at McBride Bay, South Hero, only three small specimens were 

 found. Valcour island, therefore, is the most northern locality in 

 the Champlain area at which specimens were found in numbers 



