40 



BRITISH FOSSIL TRIGONE. 



Trigonia Woodwardi, Lycett, sp. nov. 



Shell large, ovately trigonal, depressed ; umbones elevated, pointed, recurved, placed 

 at about the anterior third of the valves ; anterior side produced, its border curved 

 elliptically with the lower border, which is lengthened and nearly straight posteally ; the 

 superior border is nearly straight, it slopes downwards obliquely, and forms only a slight 

 angle with the posteal border of the area, the lower extremity of which is pointed. The 

 escutcheon is narrow, lengthened, and concave ; its superior border is raised. The area is 

 narrow, its superior or umbonal portion forms a considerable angle with the costated 



surface of the shell ; it has three small tuberculated carinas, which become evanescent 

 posteally, and transverse irregular plications, which form near to the umbo, acute, regular, 

 small costellae. The other portion of the shell has the rows of costa3 small, widely 

 separated, nearly straight or oblique, sometimes somewhat undulated ; the tubercles in 

 the rows are numerous, rounded, closely placed, and unequal ; they become smaller, 

 crowded in the rows, cord-like and attenuated near to the anteal and lower borders ; the 

 few last-formed rows are smaller, their pallial portions curve much forwards ; about 

 twelve distinct rounded tubercles occur in each row. The lines of growth are strongly 

 defined over the whole of the shell. 



Length 4£ inches, height 3| inches, diameter through the united valves If inch. 



