AUCELLA. 69 



Remarl-s. — The English specimens have the median part of the valve apparently- 

 less sharply marked off from the anterior and posterior parts than it is in the 

 examples figured by Hennig, but they agree in this respect with the figure given 

 by Peron. 



The specimens show some variation in obliquity and in their relative height 

 and length. The differences seen in the ornamentation are probably due, in part, 

 at any rate, to imperfections in the preservation of the surface layer of the shell. 

 Like Peron, I have seen no specimen of the right valve. 



Examples of this species are pi-eserved in the Norwich Museum, in Dr. Black- 

 more's collection, and in Mr. Brydone's collection. 



Distribution. — Zone of Actlnocamax quadratus of East and West Harnham 

 (Salisbury). Zone of Belemnitella mucronata of Clarendon (Salisbury) and Norwich. 

 Chalk of Trimingham. 



Genus — Aucella, A. Keyserlimj, 1846. 



('Eeise iu das Petschora-Laud,' p. 297.) 



Aucella volgensis, Lahusen, 1888. Plate X, figs. 1 a-c, 2 a-c. 



1888. Aucella volgensis, J. Lahusen. Ueber die russiseheu Aucelleu (Mora, du 



Comitc gcol. Euss., vol. viii. No. 1), p. 

 38, pi. iii. fi-,'s. 1—17. 



1896. — — A. P. Pavlow. Quart. Journ.Geol. See, vol. Iii, p. 549, 



pi. xxvii, fig. 1. 



1896. — — var. eadiolata, Pavlow. Ibid., p. 650, pi. x.\vii, fig. 2, 



Description. — Shell large, obliquely ovate, nnich liigher than long, moderately 

 inflated, with regularly curving margin. 



Right valve of moderate convexity, flattened. Umbo relatively small, and 

 curving only slightly. Anterior ear triangular, with n dec]), iiari'ow byssal siiuis. 

 Posterior ear indistinctly limited. 



Left valve very convex and rounded, the dorsal portion continued into a large 

 and prominent umbo which curves anteriorly, Postero-ventral part of valve pro- 

 duced and somewhat compressed. 



Surface of valves with concentric growth-ridges, sometimes produced into 

 lamellfe, and forming regular curves. 



Measurements : 



(1) (2) 



Length .... 45 .. 36 mm. 



Height of left valve (oblique) 60 . . 55 „ 

 Thickness (lioth valves) . 32 . . 22 „ 

 (1, 2) Spilsby Sandstone, Donnington. 



