FROM THE INFERIOR OOLITE. 521 



Murchis oil's ' Siluria,' for a Devonian shell, the latter, however, 

 probably not being now referable to the same genus. 



Macrodon ? rapidtjs, n. sp. Plate XVIII. figs. 2, 2 a, 3. 



Shell very transverse, flat and ovate. Umbo very anterior, small, 

 depressed, proximate, and slightly curving forward. Surface much 

 flattened on the back, decidedly concave behind the rounded line from 

 the umbo to the posterior point, and indistinctly so at the supero- 

 aDterior corner ; covered by very numerous, low, rounded rays, which 

 are frilled by multitudinous transverse markings, are separated by 

 channels of their own width, and become gradually larger towards the 

 posterior angle. A few impressed lines of growth. Anterior mar- 

 gin very convex, and posterior one extremely so, the greatest cur- 

 vature in both being in the inferior part. Inferior margin slightly 

 convex. Hinge-line much less than the transverse diameter, bluntly 

 subangular in front, curved behind, very narrow, marked by three 

 or four long, curved, transverse lines, with four very small oblique 

 teeth at each extremity. 



Dimensions. Length 16 lines, width 36 lines, depth 5 lines (for 

 one valve). 



There is a very fine specimen in the Jermyn-Street Museum, and a 

 less perfect one in the Bristol Museum, both from the Humphriesia- 

 nus-zone of Dundry. In the former, no signs of the teeth could be 

 found, and this threw great doubt on its genus, until the hinge was 

 developed in the Bristol specimen. If, as is probable, the long 

 transverse lines belong to the ligamental area, then the hinge itself 

 would be almost linear for the greatest portion of its width. 



Macrodon rasilis, n. sp. 



Shell extremely transverse, oblique, very convex. Umbones mode- 

 rately elevated, much incurved but very distant, very anterior and 

 facing forward. Hinge-area broad and somewhat excavate. Hinge- 

 line long, with several radiating teeth in front, and one long and 

 two short transverse ones behind ; extremities angular. Anterior 

 margin oblique, convex ; inferior straight ; and posterior deeply 

 eonvex. Yalves slightly concave immediately below the posterior 

 end of the hinge-line, otherwise roundly convex ; slightly depressed 

 and gaping at the centre of the inferior side. Surface smooth, ex- 

 cepting numerous irregular growth-lines. 



Dimensions of each valve, 5 lines long, 15 lines wide, and 3 lines deep. 



Locality. Bradford Abbas ; one specimen in the Bristol Museum. 



This specimen is very similar to Cucullcea elongata, Sow., Min. 

 Conch, t. 447. fig. 1, in general shape, but differs in the absence of 

 radiations. From Area sublata, D'Orb., which is figured by Thur- 

 mann and Etallon, Leth. Bruntr. t. 26. fig. 8, and is the Area lata of 

 Koch and Dunker, Verst. nordd. Oolgeb. t. 7. fig. 10, it is distin- 

 guished by its greater width, rounder form, and more anterior and 

 less pointed umbo. Area elongata, Goldf. t. 123. fig. 9, is a more 

 angular and radiated shell, and is considered to be the young form 

 of Macrodon hirsonensis, D'Arch. 



2p2 



