OSTREA. 387 



Types. — Ostracites sulcatus, Blumenbacli, from the Senonian of Salzberg near 

 Quedlinburg, is stated by Hennig to be in the Natural History Museum, Berlin. 

 Ostrea sp. Mantell, from the zone of Micraster cor-anguinum of Soutlierham near 

 Lewes, and 0. semiplana, Sowerby, from the zone of Belemnitella mucronata of 

 Norwich, are in the British Museum. 0. alseformis, Woodward, and 0. inequicostata , 

 Woodward, are from the zone of B. mucronata of Norwich ; the original of fig. 3 of 

 the former is in the Norwich Museum, but the other specimens cannot be found. 

 0. cavinata, Sowerby (in Dixon), cannot be found. 



Distribution. — Probably zone of Terebratulina lata of the South Devon coast. 



Zone of Holaster planus of the South Devon coast, Froxfield (Hants.), White 

 Hill near Goring, and Hart's Lock Wood. 



Zone of Micraster cor-testuclinarium of Stevenage, Strood, and Chatham. 



Zone of Micraster cor-anguinum of Micheldever, Witherington, Qnidhampton, 

 Foot's Cray, Southerham (Lewes), Northfleet, New Brompton, Gravesend, and 

 Litcham, Norfolk. 



Zone of Marsupites testudinarius of Ovingdean (Sussex). JJintacrinus band of 

 Taplow and the Thanet coast. 



Zone of Actinocamax quadratics of East Harnham. 



Zone of Belemnitella mucronata of Ballard Head, Fareham, Clarendon and 

 Norwich. 



Zone of Ostrea lunata of Trimingham. 



Ostrea sartjmensis, sp. nor. Plate LVIII, figs. G — 9. 



Description. — Shell thick, higher than long; slightly, moderately, or consider- 

 able inequilateral. 



Left valve very convex, with the attached surface of variable size. Area large, 

 high, curved slightly or considerably backwards. Free part of valve with small 

 radial folds, and growth-lamella?. Inner margin with a row of small pits. Right 

 valve slightly convex, with a large area ; surface (except of the earlier part) orna- 

 mented with numerous small radial ribs separated by linear furrows, and crossed 

 by growth-lamella?. 



Affinities. —The high area and the radial folds of the left valve suggest that 

 this species may be related to 0. semiplana ; it also resembles some forms of 

 0. Boucheroni. More specimens are needed in order to determine satisfactorily the 

 affinities of this form. 



Type. — In Dr. Blackmore's collection. 



Distribution. — Zone of Actinocamax quadratusoi East Harnham, near Salisbury. 



