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BRITISH FOSSIL TRIGONLE. 



regular beadlike papilla? upon the edges of the costae, more especially of their posteal 

 portions; these close-set papillae have each also a slight depression upon its middle 

 portion ; the small transverse plications upon the marginal carina have also each a row of 

 similar, more minute, papillary prominences. Apparently this ornamented surface is 

 rarely preserved ; my specimen has it only upon the right valve, and it is not distin- 

 guishable upon examples in the British Museum. I propose to designate this species T. 

 fimbriate,. T. granigera, Cont., from Upper Jurassic strata near Berne (Calcaire a Corbis), 

 has fringing papillae upon its costae, but less regular and distinct ; its costae are smaller 

 and more numerous ; the general figure is also very different, with much less convexity. 1 



Trigonia bella, Lye, sp. nov. Plate XXXII, figs. 6, 7, 8, S a. 



Founded upon fine examples of shells in different stages of growth, this species is found 

 to possess little variability in its figure and none in the ornaments of its surface ; young 

 examples have somewhat less convexity and the figure is more lengthened, as exemplified, 

 Plate XXXII, figs. 8, 8 a. Upon the whole the size is smaller than in several of the 

 larger species of the section. Its more salient features consist in the unusually great breadth 

 and prominence of the area, contrasted with the comparatively narrow costated portion of 

 the shell ; hence it follows that the posteal or siphonal border of the area has unusually 

 great length, even exceeding that of the escutcheon — a feature which is not observed in 

 any other British example of the Costata. 



Diagnostic characters. Shell convex mesially, much produced and pointed at its 

 umbonal extremity, which is only slightly, or sometimes not at all recurved. Escutcheon 

 narrow, depressed, and excavated, so that no portion of it is seen when a valve is laid 

 horizontally upon its borders and viewed from above ; its length exceeds twice its breadth 

 in the united valves ; its borders are well circumscribed by the inner carinae, which 

 form an elevated ridge on each side, fringed with large obtuse nodes. The surface of the 

 escutcheon has a numerous series of very delicate, diverging, slightly indented costellae, 

 which are remarkable for their distinctness and minuteness. 



The area is divided into two nearly equal spaces by an unusually large, elevated, and 

 nodose median carina ; the inner or anal space has a considerable and unusual amount 

 of concavity in both the valves ; its costellae, eight or nine in number, are very irregularly 

 knotted or indented ; the lower or outer space is more flattened, but also more elevated, 

 having about eight intercarinal costellae in the left valve; the right valve has only 

 three or four larger costellae, and its surface is more elevated. The marginal carina is 



1 For a detailed and instructive paper on the Inferior Oolite as exhibited at Bradford Abbas and the 

 vicinity, see the ' Somersetshire Archaeological and Natural History Society's Proceedings,' 1874, vol. xx, 

 by J. Buckman, F.G.S., &c. 



