114 



LAMELLIBRANCHIATA. 



Astarte crenata is au extremely variable species and has given rise to not a few "species"; 

 these I can only recognize as nominal, as my material contains transitions between them. The 

 specimens living in the waters of Iceland, Jan Ma\en and Greenland mnst, therefore, in my opinion, 

 be arranged under the following varieties: forma fypica^ var. snb(Tqnilatrra Sowb., var. crrbricosfata 

 j\Ic. An dr. & Forb., var. iiiflafa Hagg and var. ncnficosfafa Jeffr. 



Forma typica. 

 PI. I\', figs. 5 a, b and c. 

 Asfarfr crenata Reeve, Conchol. Icon. XIX, 1874, Astart(\ sp. 9, PI. 2, fig. 9. — Astarte oblonga 

 Sowerby, Thes. Couchyl. II, 1855, p. 781, PI. 167, fig. 19. — Astarte crenata Gray f. typica 

 Jensen, Medd. om Gronland, XXIX, 1909, p. 337. 



The shell oval, more or less convex, with numerous (ca! 50), relatively low, concentric ribs, 

 which disappear on the posterior part of the shell; periostracum light-coloured, yellowish. 



In its typical shape (PI. IV, figs. 5 a and b) it is quite characteristic, but this again is subject 

 to great changes'). The ribs may be fewer and more prominent (PI. IV, fig. 5 c), so that the boundary 

 towards var. s-ttlxrquilatera vanishes. All three dimensions are subject to considerable variation.s, as 



will be seen from the accompanying measurements: 



Height Breadth 



Locahtv Length Height Breadth 



Length Length 



Hurry Inlet 23 ""^. 17.5 ""^. 76.1 7„ 10.5 "^". 45.7 % 



Cape Hope 23.5 - 17.5 - 74.5 - 11.25- 47-9 - 



S. E. of Sabine Island 23.5 - 18.2 - 77.4 - 12.5 - 53.2 - 



— - — — 26.5 - 21.5 - 81.1 - 12 - 45.3 - 



This form occurs at East Greenland, where the Danish Expeditions 2) have taken it at the 



following places: 



Hurry Inlet 50 fm., cla>- with stones. Numerous spec. 



Cape Hope i2i - — — — 3 spec. 



Cape Tobin 120 - i spec. 



72°24' N. L., i9°42' W. L 130 - i living & 2 empt\- spec. 



72°5i' - - 20°23V2' W. L 124 - , clay. i spec, (empty). 



72°53' - - 20^36' W. L 96 - 6 - 



73°24' - - 20° - - 106 - 2 — 



S. E. of Sabine Island no - , fine clay with stones and 



gravel. 10 spec. &: some valves. 



and the Swedish Expedition of 1900 at the following places: 



72°25' N. L., i7°56' W. I^ ca. 160 fm., stones and sand. 5 spec. 



1) For some very .short and convex specimens Hagg has set up the varietv- incostata (Ark. f. Zoologi, Bd. 2, Nr. 2, 

 I9°4. P- 37' PI- I. figs. II — 12); a similar form, Hkewise with weaklv developed and very densely placed ribs, is in onr Mii.seum 

 from Unianak in West Greenland (cf. the following). 



2) A. crenata has for the rest been taken at East Greenland (Shannon Isl., 30 fm.) already in 1869—70 by "Die zweite 

 Deutsche Nordpolarfahrt" (cf. Wissenschaftl. Krgebnisse, II, 1S74, p. 252 under the name of Astarte crcbricostata). 



