230 'I'HE ICE AOK IN CANADA. 



they prob;il)ly lived in somewhat deeper and C(dder water 

 than the others. The water, I may add, on this coast is 

 so far af'l'eeted by the arctic current as to he ([uitc cold, 

 except near the shore and in shallow hays, and the species 

 ilredged in 10 to 15 fatiioms are, in general, similar lo 

 those of the Labrador coast, belonging rather to the boreal 

 than to the Acadian fauna. AVith the Mvas were cast ui) 

 shells of Solenciisii^', var. Amrrifanti^ of Carpenter, and of 

 Maehacva codata, the latter sometimes of large size, 

 though it is more abundant in the warmer water at tlie 

 head of the bay, where Piirpura Lcqullns, a rare shell on 

 this coast, also occurs on the reefs. 



It is evident that though there is no ]iassage fr(jm one 

 species into the other, the long variety of Mija fru/icatd, 

 represents the extreme limit of modification of that 

 species for a shallow and warm- water habitat, while tiie 

 small epidermis-clad variety of M. arciKiria represents its 

 extreme modification for deeper and colder water tliau 

 usual ; and along the coast at Met I., these two varieties 

 meet. 



The coldness of tlie IHeistocene seas thus ex])lains the 

 occurrence, in the upper Leda clay, of the i)eculiar small 

 and epidermis-clad variety of M. airmiria and of the 

 short form of Mya tninada. The conditions in the colder 

 parts (jf the river St. Lawrence approach in these respects 

 to those of the rieistcjcene, though they are no doulit 

 more fully realized in the arctic .seas. 



As I have remarked in my notes on the Post-pliocene, 

 the brown wrinkled epidermis-clad variety of M. arcnaria 

 ♦tccurs plentifully along with M. Uddcvalcnsis in the 

 upper Leda clay at liiviere-du-Loup. 



From llie accoinits of arctic collectors from Fal)ricius 

 downwards, it would ap[tear that in (Ireenland, as in 



