On the Mollusca of Nordland and Finmark. 267 



XXVI. — On the Distribution of the Mollusca in Depth on the 

 Coasts of Nordland and Finmark. By R. M'Andrew, F.R.S. 

 and L. Barrett, F.G.S. 



We have divided the space between high water and 200 fathoms 

 into four zones : the first, or Littoral zone includes the shore 

 between high- and low-water marks ; the Laminarian zone ex- 

 tends from low water to 20 fathoms ; the Coralline zone between 

 20 and 60 fathoms ; and the deep-sea Coral zone includes the 

 ground between 60 fathoms and the greatest depth explored, 

 which was 200 fathoms. We have given a list of the shells 

 found in each zone. 



Littoral Zone. 



The species found living at low water on the coast of Finmark 

 are all Arctic, the same species being inhabitants of the lit- 

 toral zone of Greenland. In Nordland, Patella vulgata, Trochus 

 tumidus and Trochus cinerarium are abundant in this zone, but 

 they do not range to Finmark or Greenland; while Buccinum 

 cyaneum and Natica clauma, abundant species in Finmark, are 

 not found farther south than the northern part of Nordland. 

 When the shore is composed of sand or mud, bivalve Mollusca 

 are most common. On a rocky coast Gasteropoda are abundant, 

 and Conchifera scarce. Several species included in the following 

 lists ought perhaps to be considered inhabitants of the next 

 zone, though they occurred abundantly on several occasions at 

 extreme low water. 



Testacea of the Littoral Zone, 

 Shore Rock. Shore Sand. 



Natica clausa. 

 My a truncata*. 



arenaria*. 



Astarte compressa? 



arctica ? 



Cardium edule ? 



Buccinum cyaneum*. 



undatum. 



Purpura lapillus*. 



Bela turricula ? 



Littorina littorea*. 



rudis*. 



arctica*. 



gra?nlandica*. 



Lacuna vincta ? 



Rissoa ulvae *. 



Skenea planorbis*. 



Trochus tumidus. 



cinerarius. 



Margarita undulata ? 



helicina. 



Acmsea testudinalis*. 



Dendronotus arborescens. 



Mytilus edulis*. 



Crenella discors. 



Saxicava arctica. 



Note. — The asterisk indicates that the species attains its maximum of 

 development in that region; the note of interrogation imphes that the 

 species is probably a straggler. 



