18 JAMES A. GRIEG. [SEC. ARCT. EXP. FRAM 
both specimens with thick and thin valves may occur. Typical speci- 
mens of the form arctica have a length of 25—26 mm., and a height 
of 12.5—14 mm. Some specimens which may be referred to this form 
have moreover, a length of up to 38 mm., and a height of 16.5 mm. 
The form pholadis s. rugosa has a length of 46—47 mm., and a height 
of 24—25 mm. 
Lyonsia arenosa, Méuirr. 
Locality: 
July 25. 1900. The winter harbour, Havnefjord, about 20 m. Rocks and stones, 
July 26.  , West side of the entrance to Stordalen, Havnefjord, 16—20 m. Clay. 
Sept. 19. ,, Off Forvisningsdalen, Gaasefjord, 4—40 m. Clay with small stones. 
Sept. 20. , The head of the Gaasefjord, 6—40 m. Clay with small stones. 
Aug. 2. 1901. _ _ _ , about 40 m. 
Aug. 16. ,, — _ _ , about 14 m. 
In Havnefjord only a quite young specimen was obtained 7.5 mm. 
long. In Gaasefjord 10 specimens in all were collected, which were 
15-26 mm. long. The height of their shells varied from 54°/, to 
64.25 °/) of their length, while the breadth (thickness) varied between 
37.14°/, and 42°/, of their length. For purposes of comparison we 
may state that Jensen found in the case of some specimens from the 
east coast of Greenland, that the height of the shell was 51.6—62.7 °/, 
of the length and the breadth 36.9—44.7°o of the length. Some of 
the specimens from Gaasefjord measure: 
Long. 26 mm. Lat. 16.7 mm. Crass. 10.5 mm. 
% , 155 , 10 , 
8 15.5, 105 , 
% 185 , 95, 
35 , 145, 5 , 
ic . 10.5, ae 
145, 10, 65, 
15h, 95, e = 
The specimens closely resemble the description and illustration which 
Hancock gives of lyonsia gibbosa (lyonsia arenosa var. sibirica Lrcue) 
from Davis Strait. 
Thracia truncata, Turton. 
; Locality: 
July 29. 1899. The winter harbour, Havnefjord, 12m. A somewhat deformed 
specimen (Long. 18.5 mm., Lat. 14.5 mm., Crass 9 mm.). 
July 25. 1900. The winter harbour, Havnefjord, about 20 m. Rocks and stones. 
One specimen (Long. 13 mm., Lat. 10 mm., Crass 7 mm.) belongs 
to the typical form, the other on the contrary more closely 
resembles the variety devexa G. O. Sans. 
