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Plate 1. 



Fig. I. Anomia patelliformis L. 



a. The upper valve, showing the position of umbo, x i'/,. The Faeroes. 



b. The lower valve, showing the size and form of the notch, x i. South Iceland, ca. 20 fm. 



c. The upper valve from the inside, showing the two muscular impressions (one of the adductor, 

 one of the byssus muscle), x i. The Faeroes. 



— 2. Anomia squamula L. 



a. The upper valve, showing the position of the umbo, x I'/a- West Iceland (Dyrafjordr). 



b. The lower valve of the same specimen, showing the size and form of the notch, x I'/a. 



c. The upper valve from the inside, showing the two muscular impressions (one of the adductor, 

 one of the byssus muscle), x iV2- South Iceland, 58 fm. 



d. Var. aculcata Miiller. The upper valve showing the spinous surface, x I'/a. West Ice- 

 land, 19V2 fill- 



— 3. Anomia cpliippiuin I^. 



The upper valve from the inside, showing the three muscular impressions (one of the adductor, 

 two of the byssus musculature), x i. The Mediterranean. 



— 4. Pectcn islandicus Miiller. 



a. A part of the shell, to show the rasp-like structure, characteristic of the species, x 7. Of 

 a specimen from East Iceland, 35 — 55 fm. 



b. The rasp-like structure disappears on the lower part of the shell, where the radiating ribs 

 lie very close and are covered with scales, x 10. Of a specimen from West Iceland, 4—7 fm. 



c &. d. A very small specimen to show that its sculpture is quite different from that of the 

 older. X II. East Iceland, 52 — 43 fm. 



— 5. Pectcn ara/tis G m e 1 i u. 



a & b. A specimen with well marked, primary ribs, x i. S. W. of Iceland, 295 fm. (Ingolf St. 9). 

 c & d. A specimen with the radiating ribs more equally developed, x i. S. of Iceland, 268 fm. 



e. A part of the shell figured in 5d; the radiating ribs are rough from small, down-turned 

 scales (almost as in /-". islandicus, comp. fig. 4 b, but it lacks the intercostal rasp-like struc- 

 ture of the latter), x 12. 



— 6. Pectcn scploiiradidtns Miiller. 



a & b. A specimen with relatively many folds and provided with small spines, especially on 

 the left valve (var. n. scaber). x i. S. W. of Iceland, 295 fm. (Ingolf St. 9). 



c. A part of the left valve to show that the radiating striae are densely beset with sharp 

 scales. X 9. 



— 7. Pectcn frigidiis Jensen. 



a, b & e. A specimen from the Norwegian Sea, loio fm. (Ingolf vSt. 119). x lYa- 

 c &: d. A specimen from the Norwegian Sea, 1060 fm. (Ingolf St. 118). x I'/z- 



f. A very young specimen from the Ingolf St. 119. x 7. 



