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SUPPLEMENT TO THE BRITISH 



UNCERTAIN GENERA. 



The genera to which the three following minute shells should be referred is still a 

 matter of considerable uncertainty. I leave them provisionally under Spiriferina, where 

 they have been placed by Mr. Moore, but to which genus in every probability they do 

 not belong. Their extreme minuteness, and the small number of specimens I have been 

 able to examine, makes their study and examination a very difficult matter. It is to be 

 hoped, however, that with time, and under more favorable circumstances, their generic 

 position may be ascertained. 



44. Spiriferina ? oolitica, Moore. Dav., Supplementary Appendix, vol. i, p. 30, 



and Sup., PI. XI, figs. 13—15. 



Spirifera oolitica, Moore. Proceedings of the Somersetshire Archaeological and 



Natural History Society, vol. for 1854, p. 115, 

 pi. iii, figs. 13, 14. 



Sp. Char. Shell minute, transversely oval. Sometimes nearly as long as broad, but 

 usually much broader than long ; hinge-line slightly shorter than the greatest breadth of 

 shell. Valves moderately convex, without any defined fold and sinus. Dorsal valve 

 semicircular, ventral valve much deeper than the opposite one, beak comparatively large, 

 slightly incurved ; area triangular, fissure wide margined laterally by deltidial plates. 

 Surface of both valves ornamented by eight or ten rounded ribs which commence to rise 

 at some little distance from the extremity of the beak and umbo. 



Length a little more than half a line, breadth about one line. 

 Obs. After very considerable trouble I have been able to make an incomplete and 

 much enlarged drawing of the interior of the dorsal valve (Sup., PI. XI, fig. 15), in 

 which the widely separated hinge-sockets and muscular impressions are delineated. Mr. 

 Moore writes me that he is disposed to think that this form will have to be classed in 

 the genus Argiope, but I have not been able to trace in its interior any of the vertical 

 septa which, in this genus, support the loop. The muscular impressions are singularly 

 large, and from the base of the hinge-plate may be seen the points from which some kind 

 of loop or spiral appendages took rise. Along with the typical form (fig. 13) was found 

 a more circular and globose variety (fig. 14). 



