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BRITISH FOSSIL TRIGONLE. 



Trigonia Tealbyensis, Lye, sp. nov. 



A single very imperfect specimen in the Woodwardian Museum, Cambridge, is the 

 only one known to me of a beautiful species of the Quadrata obtained in the Neocomian 

 formation at Tealby, Lincolnshire. Should no other more suitable specimen occur it 

 is proposed to figure this fossil upon a future plate ; unfortunately the shells in the bed 

 of hard limestone at that locality are converted into fragile crystalline lime, which breaks 

 into fragments by the concussion of a blow with a hammer ; there is, therefore, little 

 probability that any example devoid of injury will be obtained from that bed. In the 

 present instance the posteal half of the valve has been broken away, and the figure of the 

 shell longitudinally is, therefore, rather doubtful. 



Diagnostic characters. — Shell short, inflated ; umbones much arched inwards, 

 slightly recurved, not prominent, obtuse j anterior side short, its border curved 

 elliptically with the lower border ; superior border convex. Escutcheon broad and 

 flattened, its upper border elevated, its outer or carina! border depressed with closely 

 arranged, narrow, diverging scabrous plications or rugose folds. Area narrow, flattened, 

 forming a considerable angle with the other portion of the valve. The ornamentation of 

 the umbonal portion of its surface is minute and delicate ; there is a small median 

 furrow ; the marginal and inner carinse are also very small and slightly knotted. The 

 surface of the area has numerous regular, faintly defined, small, transverse indented 

 lines. The other and by much the larger portion of the shell has the rows of nodose 

 costse numerous, concentric, and closely arranged ; the nodes upon the rows are very 

 numerous, small, perfectly regular, closely arranged, prominent, and only partially 

 rounded, as if compressed laterally in the rows or moulded by the lines of growth, which 

 are densely arranged and conspicuous over the anteal and middle portions of the valve ; 

 the rows have a slight horizontal flexure at their posteal extremities and also near to the 

 anterior border, where their nodes become indistinct or cord-like. The fragment 

 referred to has upwards of twenty rows of costae, which do not represent the entire number. 

 The convexity of the valve is very considerable ; the faintly marked features upon the 

 anteal portion of the area indicate that the posteal portion is altogether without 

 ornamentation. The short, subglobose figure suggests the possibility that it may be 

 identical with T. paradoxa, Ag. ('Trig.,' p. 46, tab. x, figs. 12, 13), known only from 

 two internal moulds, which exhibit no trace of the external ornaments ; in common with 

 our shell they appear to have no near affinities with any one of the Cretaceous Trigonia? ; 

 both are from the same formation. The French specimens of T. paradoxa are from the 

 Neocomian of Besancon. 



