On Jurassic and Cretaceous fossils from North-East Greenland. 469 



large, flat "wing". Surface with fairly coarse, concentric ribs and 

 with some fine, concentric lines. 



Greatest length of the shell 14 mm, its i)readth ca. 8 mm (meas- 

 ured at right angles to the length). 



Distribution. North-East Greenland: "Kløft Г' on Store 

 Koldewey Island (2 spec). 



Russia: in limestone deposits of the Donez-Jurassic. 



Germany: Upper Jurassic. 



33. Yoldia sp. 



A specimen of ii small Yoldia was found in one of the black 

 calcareous concretions occurring as boulders in Vesterdalen at Dan- 

 marks Havn. Unfortunately the specimen is so badly preserved, that 

 a certain determination is impossible. 



34. Macrodon Keyseriingii d'Orbigny sp. 



1846. Area elongata Sow.; Keyserling, Petschora-Land, p. 305; PI. 17, figs. 1—4. 



1850. — Keyseriingii d'Orbigny, Prodrome de Paléont., I, p. 3(i9. 



1883. Macrodon Keyseriingii d'Orb. ; Lahusen, Jurass. Bild. Rjasanschen Gouv., p. 28; 



PI. 2, figs. 14-15. 

 1905. — — — ; BoRissjAK, Pelec^'poden der Jura-Ablagerungen 



im europ. Russland, II, p. 2 and 42; PI. 1, 



figs. 5- 8. 



A left valve of a large Macrodon seems referable with certaintj^ 

 to this characteristic species. Only the inner side of the valve is 

 acces-sible for examination however. The valve is strongly arched, 

 very elongated, with very unequal sides. The anterior margin meets 

 the cardinal margin at a slightly blunt angle, and the ventral margin 

 shows a relatively deep concavity. 



Height ca. 20 mm, length 50 mm. 



A fragment of a right valve probably belongs here also. 



Distribution. North-East Greenland: "Kløft П" on Store Kolde- 

 wey Island (1 spec). ? In a loose-lying stone at "4. Sænkning" (1 spec). 



Russia: in deposits belonging to Middle Callovian — Séquanian. 



35. Macrodon Schourovskii Rouillier sp. 



1847 — 48. Cucullaea Schourovskii Rouillier, Études progr. Géol. Moscou, II, p. 428. 



PI. H, fig. 39. 



1900. Macrodon — — sp.; Pompeck.t, Jurassic Fauna of Cap 



Flora, p. 67; PI. 1, fig. 17. 



1905. — — — - ; Borissjak, Pelecypoden der Jura Ab 



lagerungen im europ. Russland, 

 II, p. 12 and 48; PI. 2, figs. 10-12. 



Only a left valve can be referred to this species. 

 The valve trapezoidal, strongly arched; the umbo somewhat in 

 front of the middle, inclined forwards rather strongly. Ventral margin 



XLV. 34 



