PLEISTOCENE FOSSILS. 229 



I have not infrequently dredged Mya truncata, visually 

 the long variety, but sometimes the short Uddevalensis 

 variety, in deep water outside the bay, but have not seen 

 it above low-water mark, though it occurs not far from 

 this line ; and, on tlie opposite side of the river St. 

 Lawrence, I have found it at Tadoussac, where the water 

 is still colder, close to low-water mark. I was not aware 

 till lately that Mya arenaria occurred on the compara- 

 tively steep and stony shore outside the bay, and it is 

 certainly not found there inside of the low-water limit. 



In 1888, however, after a heavy easterly gale, great 

 numbers of Mya arenaria, in a living state, and a few 

 specimens of M. trtoncata, were thrown up on the beach, 

 and must have been derived from the mud disturbed 

 by the breakers at no great distance outside of low- 

 water mark, or on a slight bank a little further seaward. 

 The former were all of small or moderate size, some- 

 what round and flat in form, much wrinkled and 

 covered with a thick brown epidermis which extended a 

 little way beyond the posterior end of the shell, which 

 was, however, rounded and not truncated, and destitute 

 of the corneous tube of M. truncata. Still, many of the 

 specimens might, at first sight have been mistaken for 

 M. truncata, with the tube partly broken off. This 

 enabled me, for the first time, to understand the remark 

 of Fabricius, that in Greenland the two species are so 

 similar, that but for the hinge and the tube they might 

 be confounded. With these were thrown up specimens 

 of M. truncata, which must have lived with the others, 

 the inner limit of M. truncata probably overlapping the 

 outer limit of M. arenaria. The short or Uddevalensis 

 variety of truncata was, however, very rare, only a few 

 shells in a perfectly recent state having been found, and 



