REPORT OF THE DIRECTOR 1920-21 175 



half (or more) to less than one-half the size of the Montreal specimens. 

 The Port Kent and Burlington localities are the most northerly 

 ones at which Yoldia arctica has been collected in the 

 Champlain area. The largest specimens at Port Kent vary from 

 10 mm x 7 mm to 12 mm x 8 mm; the averaged- sized specimens vary 

 from 6. 7 mm x 4.5 mm to 8.5 mm x 5.4 mm and 8 mm x 6 mm. 

 The majority of the specimens are included in the smaller sizes 

 measuring 7 mm in length and slightly under. The largest specimens 

 then are a little above one-half to three-fifths or more the size of 

 the recent and Montreal specimens, while the average-sized specimens 

 are well under one-half, and even one-third, their size. Of the 

 specimens found at Burlington and vicinity, the largest number 

 were found around Mallett's Bay, but the species was not found 

 • to be very abundant anywhere in this area. A larger number of 

 specimens would be necessary to make any more than an approximate 

 comparison with the Port Kent material; but so far as observations 

 go the average specimens of this material run as small as, and perhaps 

 smaller than, those from Port Kent. The large-sized specimens 

 are few in number and vary from 9.8 mm x 6 mm to 13.9 mm x 8 mm. 

 The average-sized specimens (the majority) vary from 5.8 mm x 4 mm 

 to 8.2 mm x 5 mm, but only a few reach the upper limit of size. In 

 the vicinity of Ottawa the specimens in general run smaller than 

 at Montreal, the largest having been collected at Ottawa. The 

 largest specimens here attain the size of 16.4 mm x 9 mm to 19 mm x 

 n mm, but the majority of the specimens vary in length from 13 mm 

 to 15 mm and in width from 8 mm to 9 mm. At Green's creek 

 along the Ottawa river, several miles below Ottawa, and at Britannia, 

 a few miles above, all the specimens found were much smaller; but 

 specimens were not found in these localities in sufficient numbers 

 to permit comparisons. 



Saxicava rugosa and Mytilus edulis were both 

 found just a few miles north of Port Henry, but Mytilus only 

 in small fragments and these very infrequent, so it is rather impossible 

 to make any conjectures as to the size of the individuals of that 

 species at this locality. Recent specimens of Saxicava 

 rugosa from Barden bay, Greenland, range from a size of 

 34.6 mm x 18.8 mm to 41 mm x 20 mm. Macoma groen- 

 1 a n d i c a was found to be by far the most abundant species in the 

 Port Henry area; while S. rugosa was found to be rare. Less 

 than twenty specimens were collected here,' the largest found 

 measuring 22 mm x 11.5 mm and the others ranging from 18.4 mm x 

 10 mm to 21 mm x 10.3 mm. The Port Henry area was very 

 carefully searched; and, while the number of specimens collected is 



