LAMELLIBRANCHIATA. 



This species has been taken by the "Ingolf" at: 



gj. ^2=: 729 fni. — 0.8° C. Fragments of 2 valves. 



jj, 1309 ■ — I ° " 8 spec, and some fragments. 



jjy 1003 - — I ° - 6 spec, and ca. 14 valves. 



jjg 1060 - —I ° - 10 spec, and ca. 50 valves. 



. JJ2 1267 - — i.i" - Fragment of i valve. 



. jjn loio - — I ° - 25 spec, and ca. 20 valves. 



. Ill 860 - — 0.9° - I spec, and 14 valves. 



. 120 885 - — I ° - 3 — - ca. 20 valves. 



- no 781 - -0.8° - 4 - 



- 102 750 - —0.9° - ca. 25 valves. 



- 103 579 - -o-6° - I spec. 



. 104 957 - —i.i" - 10 spec, and ca. 80 valves. 



. 105 762 - —0.8° - 3 — - 2 valves. 



These 13 stations all lie between Jan Mayen, Iceland and the Faeroes, with depths of 579 — 



1309 fm. and bottom-temperature of —0.6° 1.1° C. According to Friele and Grieg (I.e.) it was 



taken at 12 of the stations of the Norweg. North-Atlantic Exped., from Spitzbergen down towards the 



Fseroes and Shetland; the depths varied from 658— 1539 fm., the bottom-temperature from — 1° 1.6° C. 



It was also found again in 1900 by the "Michael Sars" N. of the Fceroes, at a depth of ca. iioofm. 

 and with a bottom-temperature of — 1.12° C. (according to Friele, I.e. 1902), likewise in 1900 by the 

 Nathorst Exped. between Greenland and Jan Mayen (72°42' N. L., i4°49' W. L.) and at depth of ca. 

 1050 fm. (19 spec). Lastly, the "Thor" in 1903 took 3 shells off N.E. Iceland at 66°i9'N.L., io°45' W. L., 

 766 fm., bottom-temp. — 0.95° C. 



Pecten frigidus must be considered the most characteristic Bivalve of the ice-cold depths of 

 the Norwegian Sea, both in regard to size of individuals and numbers. 



The variation is fairly small, being confined to some changes in the strength of the radiating 

 striae and contour of the shell. As a rule the shell is a little higher than long (PI. I, fig.s. 7 a & b), 

 sometimes the two dimensions are approximately equal (PI. I, figs. 7 c & d). The specimens figured measure : 



Height Length 



28.5 ">"'. 26.5 "'"'. 



27 - 26.5 - 



Quite small specimens have the ears of the shell comparatively enormously large, as is shown 

 in fig. 7f, which represents a specimen 2""'. long. Even in the full-grown the ears of the shell may be 

 of slightly different size (cf. figs. 7a & b with figs. 7c & d), but are yet on the whole comparatively very 

 small, by which means the species is distinguished from the nearly related I'.piidicHs Smith and 

 P.undatus V err ill and Smith (see p. 36). 



P.frigidus^ as indicated in the diagnosis, is not exactly symmetrical and it obviously rests on 

 the flattest (right) valve, as this is always "clean", whereas the left \alve is covered with Foraminifera, 

 worm-tubes, Scalpelluin etc. 



