﻿184 



BRITISH FOSSIL TRIGONLE. 



Position and Localities. The moulds figured by Agassiz are from the Neocomian 

 formation at Voray, near Besangon. The specimen figured by Pictet ('Paleont. Suisse,' 

 plate 128, figures 6 — 8) has the test preserved ; the broad area with its median groove, 

 large transverse plications, and bounding tuberculated carinas is conspicuous ; the first- 

 formed six rows of pallial varices are nodose and transverse ; they pass across the valve 

 without interruption, the succeeding rows are broken and angulated about the middle 

 of the valve ; all are nodose. 



Within the period during which these sheets were passing through the press I have 

 been favoured by the Rev. T. Wiltshire with moulds of two Trigonise from his fine 

 collection of Hunstanton fossils obtained by him in the Red Chalk (Gault) of that 

 locality. The moulds represent a short suborbicular form distinct from T. scapha, but 

 their condition of preservation will not allow of comparison with any other recognised 

 species. 



Trigonia exaltata, Lye, sp. nov. PI. XXXVIII, fig. 2 (Scaphoide^). 



Shell scaphoidal, somewhat depressed, truncated anteally, much produced posteally ; 

 umbones subanterior, much elevated, incurved, and recurved, anterior side very short, 

 forming a flattened surface anteally, curved elliptically with the lower border ; superior 

 border lengthened, concave. Escutcheon lengthened, plain, concave, its upper border 

 raised. Area narrow, flattened, traversed longitudinally by an oblique mesial furrow 

 and crossed by very numerous, irregular, wrinkled, and rugose plications which become 

 prominent at the position of the inner carina and at the median furrow ; at the outer 

 angle of the valve near to the apex is a distinct small and narrow carinal elevation, which 

 with advance of growth changes to a line of small papillated oblique elevations ; these 

 become evanescent over the posteal moiety of the valve which has no carinal elevation. 

 The other portion of the shell is characterised by a series of nearly straight, large, nodose 

 varices, about fourteen in number \ the nodes are large, and rounded near to the angle of 

 the valve ; the more posteal six rows have the nodes more cordlike or unequal and 

 irregular near to the pallial border ; the first-formed few rows of varices are oblique and 

 near to the anteal curvature of the valve are replaced by or are united irregularly with a 

 smaller, more numerous, shorter series of varices, the few first formed of which become 

 attenuated and pass across the flattened anterior surface of the valve to the pedal border ; 

 the junctions of the extremities of the two series are throughout very irregular ; and the 

 last-formed three or four posteal perpendicular rows are also very irregular. The lines of 

 growth are large and widely separated. 



Dimensions of the large specimen figured upon our plate : 



Length 5^ inches ; height 2>\ inches; thickness through the single valve 10 lines. 



