KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 48. N:0 1. 



53 



W., 27 m, hard mud (E. Nilson 1894) 6 sps, with Bryozoa, max. d. 7. — Davis 

 Strait, 64°56'N., 66°18'W., 15—30 m, sand (E. Nilson '-/lo 1894) 2 sps, max. d. 7; 

 D:o, low water, many sps, max. h. 8; ap. 5; d. 9; wh. 5 



Bank of Newfoundland, 46° 5' N., 51°44'W., 56 fms, sand, shells (Ing. & Glad. 

 Exp. > 1871) 1 sp., h. 5.3; ap. 3.;;; d. 6; wh. 5. 



Behring Island, low water (Vega Exp. 1879) 2 sps, max. h, 5.7; ap. 4; d. 

 8; wh. 4'/^; shell very solid, Fig. 27. 



Limits of formal variation: 



Spitzbergen; h. 

 80 sps ap. 

 measured d. 



wh. 



2—3 

 1.5—2.6 

 2.9—4.5 



3'A'-4 



3— 4 



2—3.4 



4— 6 

 4-4'/-2 



4— 5 

 2.3—4.1 



5- 7 

 41/1— 4V--> 



5- 6 

 3-4.5 



6- 8.0 

 4'A-5 



6—7 

 3.7—4.9 



7.3 — 10 

 4V2— 5 



7—8 

 3.8—5.5 

 8.5—10.8 



4V2-5 



9—10 

 5.2—6.2 

 10.5—12 



5'A-5'A 



max. 9.8 (Stor Fiord) 

 5.7 

 11.1 



5V. 



Greenland ; h. 

 50 sps ap. 

 measured d. 



wh. 



2— 3 



1.4—2.4 

 2.8—4.7 



3- 4 



3— 4 

 2—2.9 



3.7—5.7 



4— 4V2 



4—5 

 2.3—3.3 

 4.8—6.7 

 4'/2— 5 



5—6 

 2.7—4 

 5.5—7.7 

 5 



6—7 

 3.4—4.5 

 7.8—8.2 

 about 5 



max. 6.5 (Norsouak) max. 8 (Davis Strait) 

 4.3 5 • 

 7.9 9 

 5 5V-1 



West coast of h. 

 Scandinavia; ap. 

 50 sps d. 

 measured wh. 



2—3 

 1.3— 2 2 

 2.6—3.2 

 3'/'— 4V-' 



3— 4 

 1.9—2.8 

 3.5—5.1 



4- 4V2 



4—5 

 2 4— 3,4 

 4.5—6.8 

 5 



5-6 

 2.7—3.8 



5.7—7.7 

 5 



6-7 

 3.2—4.3 

 6.8—8.5 

 about 5 



max. 0.4 (Finmark) 



3.5 ' , 



7 



5 



h. 



Iceland ; ap. 

 40 sps d. 

 measured wh. 



2- 3 

 1.5—2.3 

 2.5—4.6 

 3ä/,-4 



3— 4 



2—3 



4— 5.6 

 4—4'/-' 



4-5 

 2.5-3.2 

 4.9—5.8 

 4'A— 5 



max. 4.6 (Berufjord) 

 3.2 

 5.8 

 47--' 



The Scandinavian specimens, especially those from the southern districts, such 

 as Bohuslän, have a comparatively small diameter (thus are more elevated) than 

 specimens from Arctic districts. 



Colour variation : var. fasciata, Jeffreys 1865, has a spiral band of reddish- 

 brown below the suture. 



Variation of the radula: This varies but slightly in the different districts. Form 

 and denticulation of the teeth is the same, and the number of uncini only is subject 

 to change. Specimens from Bohuslän (full-grown, with a diameter of 3.7) have circa 

 50 uncini (PI. 6. fig. 3); specimens from Norway (Düben; d. 5.i) have 80; those 

 from Spitzbergen (d. 9.o) about 80 (fig. 4 — 5); the specimen from Behring Island (d. 

 8) likewise circa 80; specimens from Egedesminde have usually about 80 uncini (2 

 sps, h. 5.1; d. 7 2 and h. 5.4; d. 6.6), but one especially high and narrow specimen 

 showed only 50. Young animals always have a lesser number of uncini than older 

 ones; a specimen from Sukkertoppen (d. 2.2) had only 40, and another from Mossel 

 Bay (d. 30) 50. According to Sars, 1878, young specimens have also a smaller num- 

 ber of median teeth. One specimen from Norway (Düben) had an aberrant radula 

 of the formula go . 1 . (6 . 1 . 7) . 1 . oo ; the 7th tooth exhibiting some exceptionally 

 strong denticles in the outer margin. 



