70 CRETACEOUS LAMELLIBRANCHIA. 



Affinities. — The shell in this species is larger, relatively higher, more oblique, 

 and less inflated than in A. Keyserlingiana (see below). The right valve is more 

 flattened, and its umbo is only slightly curved. The umbo of the left valve is 

 larger and more prominent. 



Remarks.- — The only specimens I have seen are internal casts from the Spilsby 

 Sandstone. The example of this species described by Pavlow as var. radiolata 

 shows faint radial ribs on the internal cast of the right valve, and a slight 

 depression on the left valve extending from the umbo to the postero-ventral 

 margin (Plate X, fig. 2). 



Types. — From the Upper Volga beds of Kaschpur (Simbirsk), Staraja-Rjasan, 

 and Olenek. The specimens figured by Pavlow are in the Sedgwick Museum and 

 are here re-figured. 



Distribution. — Spilsby Sandstone (zone of Belemnites lateralis) of Donnington. 



Aucella Keyserlingiana, Trautschold, 1868. Plate X, figs. 3a — d, 4a, b, 5. 



1837. Inoceeamus concentbicus, G. Fischer de Waldheim. Oryctographie du 



gouvernm. de Moscou, p. 177, 

 pi. xx, figs. 1—3. 

 1846. Aucella concenteica, var. bugosa, A. Keyserling. Reise in das Petscliora- 



Land, p. 300, pi. xvi, fig. 16. 

 1850. Avicula (Buchia) u. sp., F. BiJmer. Neues Jahrb. fur Min., etc., p. 393. 

 1868. Aucella Keyserlingiana, H. Trautschold. Verhandl. d. russisch-kaiser- 



lich. mineral. Gesellscli. in Peters- 

 burg, ser. 2, vol. iii, p. 250. 

 1874. — concentrica, var. rugosa, F. Toula. Mesozoiscli. Versteiu. v. d. 



Kulin-Insel (Die zweite deutsch. 

 Nordpolf., in 1869, 1870, unter 

 Kapitiin K. Koldewey), vol. ii, 

 p. 503, pi. ii, figs. 2, 3. 



1874. var. rugosissima, F. Toula. Ibid., p. 504, pi. ii, 



fig. 4. 



1875. Perna imbricatus [Bean MS.], J. Phillips, Geol. Yorks., pt. i, ed. 3, p. 247. 

 — ■ — venttstulus [Bean MS.], Phillips. Ibid., p. 247. 



1884. Avicula? teutobubgiensis, O. Weerth. Neocom. im Teutoburg. Walde 



(Palseont. Abhandl., vol. ii), 

 p. 50, pi. ix, fig. 9. 



1886. Aucella Keyseelingiana, J. Lahusen. Mem. Acad. Imp. St. Pctersbourg, 



ser. vii, vol. xxxiii, No. 7, p. 4. 



1888. — Keyseelingi, J. Lahusen. Ueber die russischen Aucellen (Mem. 



Comite geol. Buss., vol. viii, No. 1), 

 pp. 21, 40, pi. iv, figs. 18—23. 



1889. Inoceeamus venustulus et imbeicatus, G. W. Lamplugh. Quart. Journ. 



Geol. Soc, vol. xlv, p. 615. 



