OSTREA. 391 



Woodwai'd, from the zone of Ueh-injiilcllK mitrroudtn of Norwich, is in the Norwich 

 :\fu.seum (Pkte LIX, fig. U). 



Disfrihutlun. — Chalk Marl (zone of ScMcenbachia varians) of Burham and 

 Dover. ^ 



Totteruhoe Stone (zone of Ilolaster snhglohosiis) of Burwell. 



Zone of Bhi/iichoiielhi Cnvlcvl of White Nothe (Dorset), Peter's Pit (Burham) 

 and Dover. 



Zone of T('rc'hratii1ina lata of BranseomLe, "Waniford (Hants) and Beachy 

 Head. 



Zone of Micraster coy-aiKjaiuitm of Quidhampton, New Brompton, and Grays. 



Zoneoi Marsupitestesfudiiiariiis of Devizes Road (Salisbury), Taplow and West 

 Wiekham. Uintacruius band of the Thanet coast. 



Zone of Actinocamax qnadratiis of East and West Harnliani, West Meon, Mottis- 

 font, Soberton and Wintei'bourne (Berks). 



Zone of Bdemnitdla mucronata of Alderbury, Clarendon and Norwich. 



Osi'KEA BorcHEROxi; CoquanJ, 1859. Plate LX, figs. 1 — 1-"). 



1859. OsTREA BoucHERONi, H. Coiiuaiid. Bull. Soc. geol. de France, ser. 2, vol. 



xvi, p. 1007. 

 1862. — TEVESTHENsis, Coquaml. Gt'ol. Pal. i-eg. sud. Province Constantine, 



p. 227, pi. xix, figs. 7 — 13. 

 18C9. — BoucHERONi, Coquaml. Mon. Ostrea, Terr. CrJt., p. 85, pi. xxxi, 



figs. 1 — 3; pi. xxxvii, figs. 1 — 16; pi. 

 xxxviii, fig. 20. 

 1890-1. — — A.Perou. Deseript. Brach., etc., Terr. Crct. Tunisia, 



p. 142. 

 1898. — — G. Midler. Mollusk. Untersen. v. Bi-aviuschweig u. 



llsede (Abhandl. d. k. preuss. geol. 

 Laudesaust., n.f., 25), p. 11, pi. iii, 

 figs. 5—9. 



Description. — Shell variable in form, usually considerably higher than long, 

 with the anterior and posterior margins generally diverging gradually from the 

 umbo. Often the .shell is more or less nearly symmetrical, but may be irregular, 

 and with the ventral part expanded. 



Left valve very convex, with the anterior and posterior parts sloping rapidly from 

 the flank to the margin. The flank is flattened or moderately convex. Umbonal 

 region usually narrow and pointed. The attached surface is at the umbo and is 

 usually rather small but sometimes large ; when large the height of the shell may 

 be relatively small, and the form of the left valve more or less semi-cylindrical. In 



' SjKjciniens of Ostren found in the Upper Greensand of Haldon resrmble eloselv 0. inciirva. 



