LAMELLIBRANCHIATA. 





6i°i 5 ' N. L., 9°35' W. L. . ca. 475 fm. valves. 



6l ° 7' " - 9°3°' " " 14" - 12 spec. & 185 vai . 



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



61 10' - - 5°46' - - 160 - , sand with stones and shells. 2 & r 



5 miles S. S. E. of Bispen 50 - 1 



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



12 miles S. S. E. of Akralejte 150 - & 



13 miles W. by S. of Munken ca. 150 - 25 



A. sulcata has thus been taken at various places round about and in part also at the Fa 1 

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



Remarks. Compared with other Astarte species, A. sulcata 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- 

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

 35 — 42, whilst the number in typical specimens, 21 — 23""". in length, from the Fseroes is ca. 30 33 



The form may 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 adUi 



Locality Length Height Breadth 



Length Length 



East Greenland 23 mm . 18.25""". 79-3"- 11.2 ran '. 48.7 



20.25 - 15.5 - 76.5 - 9.5 ■ 46.9 ■ 



- 20.25 - 15.75 " 77- s - 8 -5 - 42 - 



Iceland 24 - 19.75 - 82 -3 - I2 -75 - 53- ] 



— 23.5 - 21 - 89.4 - 12 - 51. 1 - 



Fseroes 26 - 21.5 - 83.7 - 1:3.5 - 5 x -9 ' 



23.5 - 17-75 - 75-5 - I2 -5 ■ 53-2 - 



— 22 - l8.2 - 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 many others X. E. of Shetland, 

 at a depth of i50--22ofm. 



Height , , dth 



Length Height " lth . ~, 



5 b Length Length 



26""". 21.5 """. 82.7 '- ""• I" -' 



25 - 19.5 - 78 !1 -75 " 47 



25 - 21.75 - 87 [3 



In illustration of the variability with regard to the numbei of concentric ribs, the following 

 examples are represented on PI. IV: 



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



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



