123 



well-marked mesial oblique furrow, and is traversed transversely 

 by numerous large plications, which increase in size posteally 

 and become irregular, prominent, and wrinkled. The costated 

 portion of the valve has numerous rows of tuberculated costae 

 the first-formed six or seven rows are very closely arranged, 

 slightly curved at their two extremities ; those which succeed 

 form two series ; the anteal being somewhat irregular in their 

 arrangement, and directed somewhat obliquely downwards to the 

 middle of the valve, their posteal extremities are united about 

 the middle of the valve to another less numerous, .and somewhat 

 larger series of costse ; they approach the carina at a considerable 

 angle, and the last three or four rows pass perpendicularly down 

 to the lower border. 



Until very recently this species had remained one of the more 

 obscure and doubtful forms of Trigonia, and had it not been for 

 its fortunate discovery by Professor Buckman, at Bradford 

 Abbas, while this memoir was passing through the printer's 

 hands, " The Proceedings" would not have had the privilege of 

 being the first to record it as having been met with in the county. 



Obs. T. conjungens occurs in the Cephalopoda-bed of the 

 Inferior Oolite at Bradford Abbas. 



TRIGONIA LITERATA, Young and Bird. 



MONO. BEIT. Foss. TBIGONLE, Lyc.^ Pal. Soc., p. 64, plate xiv., figs. 1-4 



Shell subovate or ovately oblong, convex; umbones large, 

 moderately elevated, obtuse, nearly erect, placed within the 

 anterior third of the valves ; anterior side moderately produced, 

 its border curved elliptically with the lower border ; superior 

 border lengthened, nearly straight, sloping obliquely downwards, 

 and forming posteally nearly a right angle, with the posterior 

 border of the area ; escutcheon wide and somewhat concave its 

 superior border moderately raised ; area narrow, slightly convex 

 with a well-defined mesial furrow. The other portion of the 

 surface has two distinct series of tuberculated costse, this dis- 

 tinctness commences at the apices. The anteal series has the 



