25 LAMELLIBRANCHIATA. 



The Swedish Expedition of 1900 took P.inibrifcr at: 

 S. E. of Pendiikim Island (74°35'N.L.) 79 fm. i spec. 



Jan Mayen. 



In addition to at the above stations of the "Ingolf", P. iiuhrifcr lias been taken by the Norwegian 

 North-Atlantic Exped. at a depth of 263 fm. (bottoni-tenip. — 0.3" C.) and b)- the Austrian Exped. at a 

 depth of 75 — 95 fm. 



Iceland. 



In addition to at the 8 "Ingolf" stations, P. iiuhrifcr has been taken by the "Thor" at: 



63°05'N.L., 20°7'W.L 293 fm i .spec, and 10 valve.s. 



62''57' - i9°58' - 500 - . I __ . 9 _ 



The Faeroes. 



As well as N. of the Faeroes, as noted above, P. iiuhrifcr has been taken (by the "Thor") S. W. 

 of the Fseroes, at: 

 6i°i5' N. L., 9°35' W. L ca. 475 fm. 12 spec, and 25 valves. 



Remarks. The specimens to hand of Pectcn iinbrifcr from East Greenland and from Jan 

 Mayen differ from the Atlantic specimens (W., S. W. and S. of Iceland, as well as S. W. of the Fseroes) 

 in attaining to a greater size, namely 15 — 22 "'"'. for full-grown specimens, against 10 — 12 "'"\ in the 

 Atlantic, as also in the fact, that the posterior ears of the shell are relatively large (cf. in PL II figs. 

 I a, b, c, d, e and f with figs. 2 a and b). 



On the whole the Polar Sea form probably reaches a greater size than the Atlantic. The 

 specimens brought home by the Dijmphna Exped. from the Kara Sea measure up to 21 """., and Leche 

 records the maximum size from the Kara Sea as 22'""'.'); Friele and Grieg give 20'"™. as being not 

 uncommon for high-arctic specimens, whereas the species does not become more than 11 '""'. at the 

 Norwegian coast. Leche for his specimens found it convenient to set up a v^r. iiiajor\ I quite agree 

 with this and propose therefore to call the southern, smaller form van minor. So far as my experience 

 goes, the variety major also differs from the more southerh- form by having as a rule the jwsterior 

 ears of the shell relativel\- large (comp. in PI. II figs, i a — f (xnr. major) with figs. 2 a — b (var. mii/or)). 

 I am of opinion, therefore, that the forms major and minor represent geographical subspecies, connected 

 respectively with the "cold" (or transitional belt to this) and the "warm" area in the deeper regions. 2) 



Within each of these subspecies there are numerous modifications in regard to the sculpture 

 of the left valve. Posselt (I.e.) has some pertinent remarks on this point. Whilst Posselt received 

 his impressions from "a consideration of the figures cited", I have been able to observe the transitions 

 on the material before me and I may take the opportunity of illustrating these not uninteresting 

 conditions by some figures. 



') In the Vega-Exped. Veteusk. lakttagelser III, 1S83, p. 452 Leche records the .species from the Bering Sea witli 

 an even greater size, namely 30 mi"., but the specimens in question T have had the opportunity of seeing in the Riks-Museum 

 at Stockhohn, do not belong to this species. 



2) The .specimens from St. 59 and St. 143 of the Ingolf, with negative temperatures, are small but seem, to judge 

 fom the relatively large, posterior ears of the shell, to be the young of var. major. 



