On Jurassic and Cretaceous fossils from North-East Greenland. 4(59 



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

 with some fine, concentric lines. 



Greatest length of the shell 14 mm, its breadth ca. 8 mm (meas- 

 ured at right angles to the length). 



Distribution. North-East Greenland: "Kloft I" on Store 

 Koldewey Island (2 spec). 



Russia: in limestone deposits of the Donez-.Iurassic. 



Germany: Upper Jurassic. 



33. Yoldia sp. 



A specimen of a 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 Keyserlingii d'Ohbigny sp. 



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



1850. — Keyserlingii d'Ohbigny, Prodrome de Paleont., I, p. 369. 



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



PI. 2, figs. 14-15. 

 1905. — — — ; Borissjak, Pelecypoden 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 certainty 

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

 accessible 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: "Kloft IF* on Store Kolde- 

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



Russia: in deposits belonging to Middle Callovian — Sequanian. 



35. Macrodon Schourovskii Rouilmer sp. 



1847 — 48. Cucullaea Schourovskii Rouilmer, Iitudes progr. Geol. Moscou, II, p. 428. 



PI. H, fig. 39. 

 1900. Macrodon sp.; Pompeckj, Jurassic Fauna of Cap 



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

 1905. — - ; BoRissjAK,Pelecypodender,Iura 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 



