127 



Clays and in the Calcareous Grits in the neighbourhood of Wey- 

 mouth, as well as in the red pisolitic iron-rock at Abbotsbury, 

 where it is invariably deprived of its test and is ill preserved. 



TRIGONIA ELONGATA, Sow., plate ii., fig. 2. 



MONO. BRIT. Foss., TRIGONLE, Lyc. t Pal. Soo., p. 154, plate xxx., figs. 3, 

 a, b, 6. 



Damon's Geol. of Weymouth, Sup., pi. ii., figs. 1, 2, 

 1880. 



Shell ovately trigonal, short, very convex at the position of 

 the marginal carina ; umbones elevated, pointed, much arched 

 inwards, and somewhat recurved ; anterior side short, its border 

 truncated, lengthened, depressed at the junction of the valves, 

 its lower portion curved elliptically with the lower border, which 

 is short and nearly straight ; hinge border very convex and 

 short, forming a considerable angle with the siphonal border ; 

 escutcheon raised, convex, and cordate, the breadth of the united 

 valves equal to three-fourths of its length ; area very large, and 

 with the escutcheon is equal in size to the other portion of the 

 valve, which has the costse large, elevated, and only slightly 

 oblique in their general direction ; in adult forms their num- 

 ber varies from eighteen to twenty-seven. 



Obs. The typical form of this species occurs abundantly in 

 the Oxford Clay at the Breakwater, Weymouth. I found the 

 var. lata the largest of the elongate group in the Cornbrash at 

 Closworth, a locality just outside the borders of the county. 



TKIGONIA MERIANI, Agass., plate iv., fig. 2. 



MONO. BEIT. Foss. TRIGONLE, Jy0.,Pal. Soc.,p. 167, plate xxxiii, figs, 13. 



Shell acutely trigonal, very convex ; umbones produced, 

 pointed, arched inwards and recurved ; anterior side produced, 

 its border rounded elliptically with the lower border, which is 

 slightly excavated posteally ; escutcheon comparatively small, 

 depressed, flattened, with its superior border somewhat raised ; 



