09 



ARKIV FÖR ZOOLOGI. BAlSD 7. N:0 4. 



27,5; heigbt 20,6; breadth (crassitudo) of both sbells 11; thick- 

 ness in the lower margin of the shell O,:; length of the liga- 

 ment 7; distance of tbe umbones from anterior margin (per- 

 pendicularly) 17. 



For oomparison two corresponding sbells of Th. truncata 

 bave been figured. 



Thracia seytentrionalis, whicb is new to Iceland, is met 

 with only in few speeimens before. It occurs off Massachu- 

 setts, Greenland, Jan Mayen and Spitzbergen (Posselt & 

 Jensen 1899). 



There were no soft parts preserved of this species, of 

 which the anatom}^ is still unknown. 



Mya truncata Linné. 



Berufjord, 15—30 fms, clay, many sps. (most of them 

 bored), max. 1. 47 (f), living 15,5 — Hofsos, 40 fms, clay, 2 

 sps., max. 1, 4,5 — Raufarhofn, 2 — 40 fms, many sps., max. 

 1. 12 — Reykiavik, 8 fms, 1 sp., 1. 19 — Siglafjord, 12 fms, 8 

 sps., max. 1. 12 — Thistilfjord, 10 — 16 fms, sand, clay, many 

 sps., max. 1. 11 — öfjord, 50 fms, clay, 5 sps., max. 1. 9,g. — 

 Torell 1859. 



var. iiddevalleusis Forbes. 



Berufjord, 7 — 13 fms, rocks, 1 sp. (t), 1. 25. 



Saxicava riigosa Linné. 

 Arnanes, 25 fms, 16 sps., max. 1. 21,') — Berufjord, 9 — 30 

 fms, clay, stones, corals, rocks, many sps., max.^1. 27 — Hof- 

 sos, 40 fms, clay, 1 sp., 1. 16 — Raufarhofn, 2—5 fms, 5 sps., 

 max. 1. 24; D:o, 35 fms, 2 sps,, max. 1. 12 — Thistilfjord, 

 10 — 16 fms, sand, clay, 2 sps., max. 1. 13. 



II. Tabular survey of the species.^ 



^ Species with an asterisc (*) are not before mentioned from Iceland. 



