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elevated narrow ridge, from the sides of which the costse and costellse diverge, each one 

 forming a considerable angle with its corresponding ridge; the costellse are therefore 

 large, but more closely arranged than in T. ornata ; the escutcheon is smaller or 

 narrower, the costellae of the area pass across it in a similar manner. The intercostal 

 perpendicular plications are small and densely arranged ; they render the upper borders 

 of the costEe prominent and obtuse ; they constitute a much less prominent feature than 

 in the allied species T. ornata and T. Vicaryana. For comparison with T. Upwarensis 

 see that species. 



The foregoing description is founded upon specimens from the Greensand of Great 

 Haldol), in which rock the test is so fragile that an entii'e shell is rarely obtained. Our 

 figured example is of the largest dimensions. 



The Upper Greensand of Sidmouth is also a locality for T. Archiaciana, where the 

 specimens are usually ill-preserved. 



A little mould figured by Agassiz (' Trigonies,' tab. 7, figs. 4 — 6) for T. spinosa is 

 probably a small specimen of T. Arclnaciana ; it has impressions of the costae, but 

 the area and escutcheon are represented only by the scar of the posterior adductor 

 muscle. The deficiencies of the specimen rendered Agassiz' description meagre and 

 insufficient ; it was obtained in the Upper Greensand of the Undercliff, Isle of Wight. 

 Our little example (Plate XXV, fig. 10) represents a specimen obtained at the same 

 locaUty and in a condition precisely similar. Specimens in a like state of preservation 

 also occur in the Upper Greensand of Warminster. The general figure and characters 

 of the costse resemble T. Archiaciana, but a rigid scrutiny is impracticable ; there can be 

 no doubt that it is altogether distinct from T. spinosa. Of this latter species additional 

 specimens from the Upper Greensand, and deprived of the test, will be given on 

 Plate XXVIII. 



The small and insufficient figure of T. puviila, Nilsson, above referred to, only enables 

 me to quote it doubtfully as probably representing a small specimen of T. Archiaciana. 

 It was regarded by Pusch (' Pol. Palseont.,' p. 60) as a young example of T. spinosa ; the 

 costae have their features very imperfectly represented. 



French localities given by D'Orbigny are Varennes, Saulce-au-Bois, Mont Blainville 

 Seignelay. 



Trigonia Vicaryana, Lye, sp. nov. Plate XXV, figs. 8, 9. 



Shell ovately elongated, convex, produced and pointed at the umbones, depressed 

 posteally; umbones subanterior, elevated, pointed, recurved; anterior side short, its 

 border curved eUiptically with the lower border ; superior border nearly straight, rounded 

 posteally with the wide siphonal border. Area wide, flattened, its surface together with 



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