126 GREY CHALK MARL. 



Tab. xxiv. fig. 6. Perspective view of a cast placed in an inverted po- 

 sition, to shew the radiated costae on the base of the volutions. 



Locahties. Middleham, Stoneham. 



It is worthy of remark, that this is the only species found in these 

 localities, while at Hamsey and OflPham, where the T. cosfatus, and T. 

 iindulatus, are met with, the present species does not occur. 



BIVALVES. 



The bivalves of the grey chalk marl so rarely exhibit any traces of 

 the hinge, that their generic characters are but seldom distinguishable. 

 The following are determined with as much accuracy as the imperfect 

 state of the specimens would admit. 



45. Area. Casts of a small species, about 1*2 inch wide, and 0-7 inch 

 long, have been discovered at Middleham ; the surface is marked with fine, 

 concentric, transverse striae. 



46. Venericardia ? Min. Conch. Tab. 259. 



This is a small species, with diverging longitudinal striae, and is 

 figured by Mr. Sowerby. 



Locahties. Middleham, Stoneham. 



47. Astarte. A minute species, covered with transverse striae. 

 Locality. Middleham. 



48. Avicula. A thin delicate species, allied to Avicula mediae Min. 

 Conch. Tab. 2. 



LocaHty. Hamsey. 



49. Venus .? Ringmeriensis, Tab. xxv. fig. 5. 



Suborbicular, with numerous transverse concentric striae, beaks in- 

 curved, approximate ; margin entire. 



The fine cast here represented, contains no vestige of the shell, and 

 the structure of the hinge is in consequence unknown ; as a temporary 

 distinction I have referred it to the genus Venus. 



Locality. Middleham ; unique. 



50. Cardium ? decussatum, Tab. xxv. fig. 3. 



