SHELLS FOUND IN THE DWINA AND YAGA DEPOSITS. 
329 
valves often adherent; and the whole, even when blanched, are generally in an 
excellent state of preservation. The collection we made (the work of two or three 
hours) has been examined by Dr. Beck of Copenhagen, Mr. Smith of Jordan Hill, 
Scotland, Mr. Lyell and Mr. G. Sowerby, all of them well versed in the forms of 
shells which occur in raised sea-beds. 
Dr. Beck considers all the species examined by him (fifteen in number) to be 
identical with those now existing in northern seas which range from 42° to 84° 
north latitude. Mr. Smith, on the contrary, believes that though many of these 
species are recent, some are of peculiar varieties now found in desiccated and ele- 
vated sea-beaches only, such as those to which he has given so much attention on 
the banks of the Clyde and the western shores of Scotland. Mr. Lyell entertains 
the same view, and at once recognizes the group as identical with that which he 
had described from Uddevalla in Sweden. Lastly, Mr. G Sowerby, differing from 
Mr. Smith in a few specific identifications, is also of opinion, that the shells of 
which we now subjoin a description, though on the whole an association of exist- 
ing species, have yet among them forms seldom, if ever, found except in raised 
sea bottoms of a sub-fossil character. 
4. Pec. ten Islandieus. 
List of Shells found upon the Dwina and at Ust-Vaga, named by Mr. Smith 
and Dr. Beck, with remarks by Mr. G. Sowerby. 
1. Saxicava arctica ( Striatella arctica, Linn., Mya byssifera, O. Fbr.). — Maybe regarded as a distinct species 
from S. rugosa ; but it is also found living from the Arctic regions to 54° north latitude. 
2. Mya truncata, Linn. — Recent in northern seas ; fossil in many localities. (Uddevalla, &c.) 
2 a. Mya ?. — It is difficult to decide whether or not this should be regarded as merely a variety of the last, 
or a distinct species. It is found fossil in several localities, but I doubt if it has been found recent. 
3. Littorina littorea, Ferr. — A very abundant recent species between 74° and 42° north latitude. 
{ Recent ; Newfoundland, and to 50° north latitude. 
Fossil; Clyde, Bute (Uddevalla). 
5. Nucula rostrata, Lam. — A living northern form = N. oblonga of Mr. Smith’s list. 
6. Tellina calc area, Chemn. — Also living in northern latitudes, towards 60° north latitude. (I* ossil at Udde- 
valla, &c.) 
7. TellinaGrmnlandica "1 Both these fossil species of Ust-Vaga are widely diffused in a living state. (Fossil 
8. Mytilus ednlis J at Uddevalla, &c.) 
9. Cardium ciliatum ?, O. Fbr. Faun. Gr. (C. Islandicum, Chemn.)-If this be the Cardium ciUatum, we are 
entirely unacquainted with that species in England. The form, as far as may be judged from the very 
incomplete specimens, approaches nearer to some Australian than to northern forms. It is very dif- 
ferent from any northern form that I am acquainted with. 
10. Cardium Grcenlandicum. — Probably the same as the recent species. 
11. Cardium edule, Linn. — Ranges to 42° north latitude. 
12. Astarte Borealis, Nilsson ( Crassina Withami, Smith).— Recent northern species, 60° north latitude ; fossil 
but not recent in the Clyde (Dr. Beck identifies it with A. semisulcata. Gray). 
