On Jurassic and Cretaceous fossils from North-East Greenland. 4()1 



18. Aucella concentrica Fischeb sp. (non Kkyserling, 



non Eichwalu). 

 PI. XXX11, figs. 9 and 10. 



1830—37. Inoceramus concenlricus Fischeh DB Wai.dheim, Oryctographie du Gouver- 



nement de Moscou, p. 177; PI. 20, figs. 1-3. 

 1888. Aucella piriformis Lahusen (pars), Ueber <lie russischen Aucellen. p. 42; PI. 5, 



figs. 1-2. 

 1907. — concentrica Fisch.; Pavi.ow, Enchainement etc., p. 66; PI. 5, figs. 27- 28. 



Numerous specimens of this species are present, all from Aucella- 

 bjerget, where they occur in a yellowish-white shell-hreccia, which 

 seems to he almost exclusively formed of larger and smaller speci- 

 mens of this species. 



Oviform, very oblique. The two valves very different. The left 

 strongly inflated, slightly elongated hehind; the margins at the heak 

 almost straight, continuing evenly through the lateral margins into 

 the almost semicircular ventral margin; the heak pointed, inclined 

 strongly inwards and somewhat backwards. The right valve con- 

 siderably less arched, almost circular, but a little oblique and with 

 projecting and pointed beak, which is bent slightly forwards. — 

 Surface of the casts in the neighbourhood of the beak smooth or 

 with few, faint, concentric folds; further down towards the ventral 

 margin well-developed, fairly sharp, concentric folds; the folds of the 

 left valve liner and denser than those of the right. 



The following measurements are of two valves from different' 



shells: 



Left valve Right valve 



Length ca. 45 mm. ca. 33 mm. 



Breadth - 34 - 31 — 



Thickness 18 — 8 



Angle at umbo ca. 80°. ca. 95°. 



The specimens agree well with Pavlow's description and figures, 

 among other things also in the fact, that smaller right valves have 

 a more triangular outline. 



Distribution. North-East Greenland; Aucellabjerget on Store 

 Koldewey Island (very numerous specimens). 



Russia: in the zone with Pohiptijchileii polyptychic. 



Germany: in Neocomian deposits. 



A number of small specimens of an Aucella were found in 2 of 

 the black calcareous concretions occurring as boulders in the neigh- 

 bourhood of Danmarks Havn. They are unfortunately too small and 

 imperfect for the species to be determined. They seem to show some 

 resemblance however to ,4. terebratuloides. 



