﻿SCABR^. 143 



surface ornaments, excepting that the pallial costae are much more widely separated and 

 have greater curvature, forming much smaller angles with the costellae upon the area ; 

 their upper borders are also sharply spined ; the escutcheon is not seen upon the same 

 figure, which proves that its surface is much depressed ; the umbones are less produced 

 and pointed than in our species. 



T. crenifera, Stoliczka ('Mem. Geol. Survey of India,' vol. iii, p. 318, pi. 15, figs. 

 13, 13 «), from Cretaceous Rocks of Southern India, is nearly allied to our species in its 

 surface ornaments, but differs considerably in the general figure, which is much 

 shorter, or subquadrate ; the dimensions are also much smaller. 



The name is intended as an acknowledgment of important assistance aff'orded me by 

 Wm. Vicary, Esq., F.G.S., in the loan of Tric/onia from the Greensands of the Blackdown 

 and Haldon districts, of which his extensive and valuable collections of Devonshire fossils 

 have supplied ample and instructive materials. 



Trigonia Upwarensis, Lye, sp. nov. Plate XXIII, figs. 8, 9. 



Trigonia spinosa, J. F. Walker. On some Coprolite Workings in the Fens ; Geological 



Magazine, vol. iv, p. 310, 18G7. 



Shell suborbicular or subovate, convex ; umbones large, obtuse, little elevated, and 

 slightly recurved ; angle of the valve well defined, not prominent, much curved ; hinge- 

 border somewhat concave, sloping obhquely, its extremity forming an obtuse angle with 

 the siphonal border, the length of which is about equal to the hinge-border ; the anterior 

 and lower borders are curved elliptically, forming an extremity somewhat pointed 

 posteally at the junction with the siphonal border. The escutcheon is short and concave, 

 of less breadth than the area ; its surface and also that of the area is traversed by 

 numerous, closely arranged, transverse, depressed, but rounded, scabrous costellae ; their 

 outer extremities are in contact at the angle of the valve with the posteal attenuated 

 extremities of the costae ; the latter are somewhat less numerous and larger than the 

 costellae, with which they form considerable angles. The sides of the valves have the 

 rows of costae (twenty-four in full-sized forms) narrow, little elevated, their summits 

 rounded, their sides with closely placed perpendicular plications ; the extremities of the 

 rows are attenuated and curve upwards ; the posteal extremities more especially curve 

 upwards perpendicularly to the angle of the valve. Occasionally the lines of growth are 

 strongly defined near the pallial border; they impress the costae and obliterate the 

 perpendicular plications ; they also become conspicuous on the area. 



Young specimens have less convexity and are more pointed at both of their 



