niiAcnioi'onA. 123 



17. TllKCIDIUM MOOREI. 



SlirU sul)(iiiii(lniti', sniootli, attiicliod l)y the wliok- surfiice' of 

 tlie ventral valve ; valves sli<;litly indented in front ; front 

 marf^ins much thiekened, steei); dorsal valve almost flat; lower 

 valve with a well-defined trianj^ular area ; deltidium lar^re, ele- 

 vated. Lon. l', lat. li, alt. 1 line. 



Thecidea Moorei, Davidson, 1851, Mon. Ool. Brach. \). \'A. pi. 1. 



f. 10. 

 Fossil. Lias {Murlstonc). llminster, attached to Rlii/nchonella'. 



18. TiiFxiniuM Deslongchami'sh. 



Shell irregularly oblong, smooth, attached by the truncated 

 beak of the ventral valve ; ventral valve deej) ; area wide, short 

 and irregular ; deltidium indistinct ; dorsal valre subcircular, 

 slightly convex, its interior siu'face siu-rounded by a broad, gra- 

 nulated l)order ; a single central sej)tura divides the brachial ca- 

 vities, in each of which there is a granul.ated lobe. Lon. 2, 

 lat. li, alt. li lines. 



Thecidea Deslongchampsii, Davidson, 1852, Ann. Nat. Hist. 



April, pi. 14. f. (J-y. 

 Fossil. Lias. Normandy. 



G2 



