jig LAMELLIBRANCHIATA. 



Jeffreys, Proc. Zool. Soc. 1881, p. 711, PL 61, fig. 9; Posselt, Medd. om Gronland, XIX, 

 1895, p. 70; Friele & Grieg, Norw. North-Atl. Exped., Zoology, Moll. Ill, 1901, p. 25; 

 Friele, Bergeus Museums Aarbog, 1902, No. 3, p. 4. -- Astarte crcnata Gray var. acuti- 

 costata Jensen, Medd. om Gronland, XXIX, 1909, p. 338; Grieg, in Due d'Orleans, Croisiere 

 oceanographique, 1909, p. 534. 



The form almost as in the foregoing variety, forming a shorter or longer, oblique quadrangle 

 netimes a rhomb), more or less convex; the concentric ribs numerous (ca. 25 — 40), strong and more 

 or less sharp, in part lamellar and imbricate. Periostracum yellow. Maximum length 13 mm . 



In its typical development, with lamella-like, somewhat imbricate folds it is a very charac- 

 teristic form, which might well be taken as a "good" species, but there are transitions, which with 

 their more rounded ribs connect it with the preceding variety and through this with the more diver- 

 gent forms of the species crcnata Gray. I can thus agree with the view put forward by Friele in 

 the year 1879 (I.e.), that Astarte acuticostata Jeffreys is only a pygmy form of A. crcnata Gray 1 ); 

 it comes very near especially to the var. inflata and may be regarded as a form derived from this 

 and connected with deeper water I have therefore taken the advanced step of including the present 

 form as a variety under A. crcnata, whereas Friele, the last time he has mentioned it (I.e. 1902), 

 still retains the distinct specific name A. acuticostata. 



For the rest, it is also rather variable however in regard to form. The anterior end, for 

 example, may sometimes be very short, sloping abruptly downwards, sometimes more projecting; the 

 posterior end is frequently high as if slightly expanded, but at other times the greatest height lies 

 further forward. Some measurements will illustrate the variation in the proportions: 



Height Breadth 



Length Height Breadth 



Length Length 



Ingolf St. 116 13 """. 11 ""». 84.6 °/ 7.5 mm . 57.7 °/ 



12.3 - IO - 81.3 - 7 - 56.9 - 



- IC-6 12 - IO - 83.3 - 6.3 - 52.5 - 



In addition to from the "Ingolf stations mentioned above, it is also present from East 

 ( '. r e e 11 1 a n d, from : 



X. of Stewart Island 158 fm., clay with stones. 2 spec. 



Fleming Inlet 118 - , clay. 1 — 



At East Greenland it has also been taken by the "Belgica" at: 



75"5 s o N. E., i4°o8' W. L 158 fm., bottom-temp. 0.40 C. 1 spec. 



Further, we have it from: 



70°32'X. E, 8°io'W. E. (S. of Jan Mayen) 470 fm. 1 spec. 



6 3 c °3' N - L., 9 28'W. L. (N.W. of Fasroes). 275 - , botm.-temp. 0.97 C. 1 spec. &. 1 valve. 



) Against this we have seemingly Friele and Jeffreys' statement, that the inner margin in A. acuticostata is 

 smooth, but in my material I have found specimens with creuulated margin. 



