474 -J- I"*- J- R^'^'N- 



is so great — among other things in the characteristic position of 

 tlie umbo — that I venture to refer the specimen to A. retrotracta. 



Distribution. North-East Greenland: at "4. Sænkning" on 

 Store Koldewey Island (1 left valve). 



Russia: in "3. Etage" at Moscow. 



42. Tancredia curtansata Рнил>п^н sp. 



(1829) 183Г). Corbula curtansata Phillips, Geolog}- of Yorkshire. I. PI. 3, lig. 27. 

 18.i4. Tancredia — — ; Morris and Lycett, Mollusca from the 



Great Oolite. III. p. 93; PI. 13, fig. 7. 



The shell rounded, obliquely triangular. The umbo somewhat 

 behind the middle, little projecting. The anterior part of the shell 

 compressed, j)ointed; the posterior })art moderately arched. The 

 margin in front of the umbo concave; the posterior margin convex, 

 somewhat blunt, the ventral margin ел'еп1у curved. The hinge with 

 a cardinal tooth and a long, posterior, lateral tooth in each valve. 

 The surface of the shell with fine and coarse lines of growth. 



A cast of a right shell: height 22 mm, length ca. 33 mm and 

 thickness ca. ô"ô mm. 



Distribution. North- E a s t G r e e n 1 a n d : in loose-lying stones 

 at "4. Sænkning" on Store Koldewey Island (2 \alves). 



England: in Great Oolite and Coralline Oolite. 



43. Tancredia planata Morris l^ Lvcktt. 

 PI. XXXIII, fig. 10. 



1854. Tancredia planata Morris & Lycett; Mollusca from the Great Oolite. III. 



p. 94; PI. 13, fig. U). 



Some casts, one of which is almost perfect, seem to agree well 

 with Morris and Lyckit's above-cited description and figures (espe- 

 cially with lig. 10 b). 



The shell triangiilar-OYal, fairly tlat. The umbo small, almost 

 in the middle. The cardinal margin in front of the umbo slightly 

 concave, behind the umbo slightly convex. The anterior margin 

 rounded; the posterior margin likewise rounded, slightly truncate; 

 the A'entral margin evenly curved. The hinge not visible for examina- 

 tion. 



The cast of a left valve: height 17 mm, length 25 mm. 



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

 Koldewey Island (1 spec). In free-lying stones at "4. Sænkning" on 

 the same island (2 si)ec.). 



England: (ireat Oolite. 



