PLEISTOCENE FOSSILS. 229 



I have not infrequently dredged Mjid truiicata, usually 

 tlie long variety, l)ut sonietime.s the sliort Uddevalensis 

 variety, in deep water outside the ])ay, hut Imve not seen 

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

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

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

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

 till lately that Alifa arcitarit/ occurred on the compara- 

 tively steej) and stony shore outside the liay, and it is 

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



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

 numhers of 3Ii/a an,i<n-i(i, in a living state, and a few 

 specimens of M. trinicata, were thrown u]) on the beach, 

 c'lnd must have been derived from the nnul disturbed 

 by the In'eakers at no great distance outside of low- 

 water mark, or on a slight l)ank a little further seaward. 

 1'he former wore all of small or moderate size, some- 

 what round and Hat in form, much wrinkled and 

 covered witii 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 tul)e of ^[. fnincatn. Still, many of the 

 specimens might, at first sight have been mistaken for 

 M. truncafa, witli the tulie ])artly Ijroken oil'. This 

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

 of Fabricius, that in (rreenland the two species are so 

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

 l)e confounded. "With these were thrown u]) specimens 

 of M. trunmta, wiiich nmst have lived with the others, 

 the inner limit of M. triincafu probably overla])ping the 

 outer limit of M. arenarid. The short or Uddevalensis 

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

 siiolls in a perfectly recent state having been found, and 



