LAMELLIBRANCHIATA. 



107 



6i°i5' N. L., 9°35' W. L ca. 475 fni. go valves. 



61° 7' - - 9°3o' - - 440 - 12 spec. & 185 valves. 



61° 9' - - 7°54' - - 181 - , sand and shells. 4 — & 2 — 



6i''io' - - 5°46' - - 160 - , sand with stones and shell.s. 2 — ^ & i — 



5 miles S. S. E. of Bispen 50 - i — 



16 miles E. by S. of south point of Nolso ca. 80 - 2 — & 9 — 



12 miles S. S. E. of Akralejte 150 - 70 — & 42 — 



13 miles W. by S. of JMunken ca. 150 - 25 — 



y4. sulcata has thus been taken at various places round about and in part also at the Faeroes 

 at depths of (12) 20—440 fni. It reaches a length up to 29 """. 



Remarks. Compared with other Astarte species, A. sulcafa is subject to comparatively little 

 variation, so far as the present geographical region is concerned. The most important variation — 

 so far as I can see — consists in a tendency of the number of ribs to increase somewhat in the 

 western part of the geographical region of the species; in specimens from off the south-eastern Green- 

 laud the ribs are so dense, that their number — in specimens of 19 — 23 "'"'. in length — amounts to ca. 

 35 — 42, whilst the number in t>pical specimens, 21 — 23""". in length, from the Faeroes is ca. 30—33. 



The form ma}' vary somewhat, as will be seen from the following measurements of some spe- 

 cimens, most different from one another in regard to the three dimensions: 



Height , Breadth 



Locality Length Height Breadth — 



^ 00 Length Length 



East Greenland 23 "■"'. 18.25™". 79-3 °/o 11.2""". 487% 



— — 20.25 - 15.5 - 76-5 - 9-5 - 46-9 - 



- - 20.25- 15-75 - 77-8 - 8.5 - 42 - 



Iceland 24 - 19.75 - 82.3 - 12.75 - 53-i - 



— 23.5 - 21 - 89.4 - 12 - 51.1 - 



Faeroes 26 - 21.5 - 82.7 - 13.5 - 5i-9 - 



— 23.5 - 17.75 - 75-5 - 12.5 - 53.2 - 



— 22 - 18.2 - 82.7 - 12 - 54.5 - 



As a further illustration of the change of form in this species as a whole, I may give here 

 the measurements of 3 specimens, which I have dredged along with man}- others N. E. of Shetland, 



at a depth of 150- 220 fm. 



Height Breadth 



Length Height ^^^^ Breadth ^^^^ 



26-™. 21.5 ■""'. 82.7% 12 ■■■■". 46.2% 



25 - 19-5 - 78 - 11-75 - 47 - 



25 - 21.75 - 87 - 13 - 52 - 



In illustration of the variabilit)- with regard to the number of concentric ribs, the following 

 examples are represented on PI. IV: 



Fig. 3 a. A typical specimen from the Faeroes, 



Fig. 3 c. A specimen with comparatively closely-placed ribs, from East Greenland. 



14* 



