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



18, Aucella concentrica Fischkh sp. (non Keyseiujn(;, 



non Eichwald). 



PI. XXXII. figs, i) and 10. 



]S;{U — .'i7. Iiioceramiis concentriciis Fischeh uk Waldheim, Oryctographie du Gouver- 

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

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



figs. 1^2. 

 1907. — concentrica Fisch.; Pavlow, Knchainenient etc., p. (Hi ; PI. ô, figs. 27-28. 



Nnmerous specimens оГ this species are present, all from Aucella- 

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

 seems to be 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 behind; the margins at the beak 

 almost straight, continuing evenly through the lateral margins into 

 the almost semicircular ventral margin; the beak 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 finer and denser' than those of the right. 



The Ibllowing measurements are of two valves from difterent 



shells: 



Left valve Right valve 



Length ca. 45 mm. ca. 38 mm. 



Breadth - 84 — 81 — 



Thickness 18 — 8 — 



Angle at umbo ca. 80°. ca. 95°. 



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

 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 Polijptychites polijptijclms. 



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 A. terehratiiloides. 



