124 



rows very numerous, small and extremely irregular ; the rows 

 are sometimes partially united to the larger posteal series, or 

 altogether separated from them. 



Obs. A single specimen of this rare shell was found by Pro- 

 fessor Buckman in the same quarry as T. conjungens. It is prob- 

 able that the harder beds of Limestone in the Oolite Sands of 

 the neighbourhood may be found to yield this species. 



COSTAT-E. 



TRIQONIA COSTATA, Sow., plate i., fig. 3. 



MONO. BEIT. Foss., TEIGONLE, Lye., Pal. Soc. p. 147, plate xxix., figs 5-10. 



Shell sub-trigonal, very convex near the divisional angle of 

 the valve, and near the apex is rather depressed posteally ; umbo 

 prominent, pointed, incurved, and somewhat recurved ; anterior 

 side a little produced, its border truncated; the escutcheon is 

 flattened and depressed, its breadth with the valves united exceeds 

 its length ; the area is large and flattened, each portion having 

 from three to five costellse. The rest of the shell has about 

 twenty-four large plain costae, all of which originate at the 

 anterior border. 



Obs. Trigonia costata has a considerable vertical extensioni 

 ranging from the Inferior Oolite to the Cornbrash. It occurs 

 frequently at Bradford Abbas and Burton Bradstock, and I have 

 met with it, in the Cornbrash of Closworth. 



TRIGONIA SCTJLPTA, Lye., plate i., fig. 4. 



MONO. BEIT. Foss., TEIGONLS!, Lye., Pal. Soc., p. 157, plate xxxiv., figs. 

 1, 2, 2a. 

 Geological Journal, vol. 35, p. 743-1879. 



Shell subovate or ovately oblong, moderately convex, umbones 

 prominent, pointed, subanterior, and slightly recurved, anterior 

 side short, its border curved elliptically with the lower border 

 superior "border straight and lengthened j the escutcheon is also 



