]4 BRITISH POSSIL TRIGONIyE. 



Inferior Oolite of Rodborough Hill, is apparently a dwarfed specimen. Although only 

 nine lines in length, it has formed seven transverse or oblique tuberculatcd costae, 

 and has commenced to develop the posteal ones. The specimen (fig. 4) from the Upper 

 Trigonia-grit of the same locality is about half the adult size and has just commenced to 

 develop the posteal costsc. 



The present examples, together with those previously figured, will, I think, amply 

 illustrate this large species, which is apparently more rare in the Cottcswolds than in 

 Oxfordshire. 



Trigonia Arduenna, var. Migaux and Smmage (not Buvignier). Trigon. Supplement, 



Plate I, fig. G. 



Descr. de quelques especes nouvelles de I'Etage Bathonien du Bas-Boulonnais, par 

 MM. E. Rigaux et W. Sauvage, Mem. de la Societo Acadcmique de Boulogne, pi. iv, 

 fig. 4, Dec, 1867. 



I have no doubt that the fragment herewith figured from the Inferior Oolite of Hook 

 Norton (beds B and C) is identical with the shell figured by Messrs. Rigaux and 

 Sauvage from the Clypeus-grit of the Bas-Boulonnais, which they regard as a variety of 

 the small species figured by Buvignier from the Oxfordian beds of the Ardennes. I 

 decidedly object, however, to the identification of this with the Oxfordian species, to which 

 I think it is only remotely allied ; the latter is evidently a much smaller and more convex 

 species with very numerous small anteal costa3, and therefore altogether distinct from the 

 much larger and more flattened shell of the Inferior Oolite. It may be hoped that other 

 and more satisfactory specimens will be obtained in Oxfordshire ; but at present I can 

 only figure the present fragment, which, although so imperfect, is highly characteristic, 

 and I believe should be separated as a species from Buvignier's little shell. 



Trigonia Guisei, Lycett., sp. nov. Trigon. Supplement, Plate III, figs. 1, 1 <?, 2, 3, 



3 a, 4, 5, 6. 



Shell ovately oblong, lengthened, having considerable convexity anteally and mesially, 

 depressed posteally ; umbones large, recurved, antero-mcsial, or placed within the anterior 

 third of the valve ; area much lengthened, narrow, flattened, bounded by two incon- 

 spicuous carinas almost throughout its length ; the marginal carina is entirely plain, the 

 inner carina is minutely papillated ; there is a small median furrow which on its outer 

 side forms a narrow ridge. The escutcheon is much lengthened and excavated, forming 



