CLAVELLAM. 41 



It is distinguished from T. clavellata and also from T. perlata by its more depressed 

 figure, by the more produced anterior side, by the straightness of the lower border, by 

 the unusually narrow area, by the straight, equal, or slightly undulated rows of costae, 

 which also have the tubercles smaller, more numerous, and more equal in size, so that the 

 surface of that portion is remarkably wide, flattened, and uniform in its aspect. The 

 costae approach the small marginal carina nearly at right angles to it. 



Compared with T. Pellati, it is less lengthened, and its rows of costae are more 

 numerous and less curved. 



T. Woodwardi has occurred rarely in the Kimmeridge Clay of Dorsetshire and of 

 Wootton Basset, Wilts. Two specimens from the latter locality are in the British 

 Museum, numbered 66, 126, but their state of preservation is only indifferent. Fine 

 examples from the same formation at Villersville, near to Honfleur, are also in the 

 Museum collection. 



Trigonia Pellati, Mun. dial. Plate VII, figs. 1, 2, a, h ; PI, XI, fig. 1. 



Trigonia Pellati, Munier Ckalmas. Bull. Soc. Linn, de Normandie, 1865, torn, ix, 



pi. iv, fig. 4. 



— — Hebert. Bull, de la Soc. Geol. de France, 2nd ser., 1865, torn, xxiii, 



p. 216. 



— — Be Loriol et Pellat. Monogr. Paleont. et Geol. de l'Etage Port- 



landien des envir. de Boulogne-sur-Mer, 

 1866, tab. viii, fig. 4. 



Shell oblong, inordinately elongated, wide upon the superior, depressed or wedge- 

 shaped towards the inferior border ; umbones near to the anteal extremity of the valves, 

 obtuse, much incurved and depressed, anterior side very short, truncated, with consider- 

 able convexity, its border curved elliptically with the lower border which is very long 

 and straight ; the superior border is also very long, its border is slightly concave, its 

 posteal extremity forms an obtuse angle with the posteal border of the area, and termi- 

 nates with its extremity somewhat pointed and much produced. The area has great 

 length, and slightly convex, with a well-marked mesial furrow bordering a line of minute 

 tubercles and bounded by two delicately traced and minutely tuberculated carinas, which 

 posteally become transverse, irregular plications. The escutcheon is flattened, of moderate 

 breadth, and unusually lengthened ; the ligamental fossa also partakes of the general 

 lengthening of the superior border ; the area has transverse, irregular plications, which 

 become large posteally. The sides of the valves are very narrow, and have a few rows of 

 very distantly arranged, oblique, tuberculated costae ; three or four of the tubercles near 

 to the carina are large, rounded, pointed, and much elevated ; those upon the lower half 

 of the valve become rapidly smaller and more depressed ; their rows curve anteally almost 



6 



