﻿CLAVELLAT^. 49 



Trigonia complanata, Li/cetf, sp. nov. Plate VII, fig. 3. 



Shell ovately oblong, depressed ; umbones small, pointed, anterior ; anterior side 

 very short, curved elliptically with the lower border ; posteal extremity produced and 

 pointed ; area very large, flattened, its surface is equal to two fifths of the entire valve ; 

 hinge-border lengthened, and nearly horizontal ; bounding carinae small, impressed by 

 irregular, small, transverse plications, whicli also extend across the area ; there is also a 

 slight mesial furrow, but the two portions of the area are upon the same plane. 

 Escutcheon large and flattened, its superior border is raised ; the other portion of the 

 surface has about thirteen rows of small, tuberculated, oblique, and nearly straight costEE, 

 each of which has about seven small depressed tubercles. 



The length is one third greater than the height ; it is also nearly equal to three times 

 the diameter through the united valves. 



The lines of growth are strongly marked, they modify both the figures of the tubercles 

 and the surface of the area. 



This clavellated species is remarkable for the unusual depression of the valves, for the 

 very short, wedge-like, anterior side, for the lengthened figm-e posteally, for the un- 

 usually large size of the flattened area, and for the small depressed tubercles upon the 

 straight rows of costse which approach the carina at a right angle. These several charac- 

 teristic features also separate it from T. davdlata, T. perlata, T. Voltzii, and T. corallina ; 

 other examples of the section are more remotely allied. 



Stratigraplmal positions and localities. A few specimens, for the most part deprived 

 of the test, have been obtained in the Kelloway Rock of Scarborough. The British 

 Museum has finely preserved examples from the Oxford Clay of Normandy. 



Trigonia Ramsayi, Wright. Plate VI, fig. 6. 



Tkigonia Ramsayi, Wright. On Upper Lias Sands, Quart. Jour. Geol. Soc, 1856, 



vol. xii, p. 323. 

 — — Lycett. Cotteswold Hills Handbook, 1857, p. 26, pi. i, fig. 8. 



Shell ovately oblong, convex, short anteally, lengthened, and somewhat attenuated 

 posteally ; umbones small, obtuse, erect, placed nearly upon the line of the anterior 

 border, so that the superior border represents almost the entire length of the shell ; the 

 lengthened lower border has only a slight curvature, and the superior border is slightly 

 concave. The area is narrow, and shghtly convex ; it is bounded by two very small, but 

 distinct and minutely tuberculated carinse, and traversed longitudinally by an incon- 



7 



