82 CRETACEOUS LAMELLIBRANCHIA. 
TrigoniA scapricota, Lycett, 1875. 
1875. Lycett, p. 130, pl. xxvu, figs. 4, 5. 
Remarks.—This form is very closely connected with 1. caudata from the Lower 
Greensand—indeed, some specimens appear to be almost inseparable from that 
species; but the majority of the Upper Greensand examples have rather more 
numerous and closer ribs towards the umbo, the shell less produced posteriorly, 
and its height somewhat greater in proportion. It should, however, be noted 
that a specimen from the Aptian of the Perte-du-Rhéne, figured by Pictet and 
Renevier,' agrees perfectly with examples of 7. scabricola from Blackdown and 
Haldon. 
Types.—From Blackdown, in the Museum of Practical Geology. 
Distribution.—Greensand of Blackdown, Haldon, and Devizes. 
Triconia crenutirena, Lycett, 1877. 
1877. Lycett, p. 189, pl. xl, figs. 1, 7, 9. 
1896. A. J. Jukes-Browne and W. Hill. Quart. Journ. Geol. Soe., vol. li, p. 154. 
Remarks.—The more prominent and fewer coste, and the greater slope of the 
area and escutcheon, which Lycett regarded as features distinguishing this from 
1’. crenulatu, @Orbigny, vary considerably in different specimens, as may be seen 
by comparing Lycett’s figures 1 and 9. In one example of 7. crenulata in the 
British Museum, from Le Mans, the coste are actually fewer than in a form of 
T. crenulifera of the same size. The costellee on the area, however, seem to 
separate 1’. crenulifera from T’. crenulata; in the latter they appear to be found 
only near the anterior end of the area. 
Types.—In Mr. Me¥er’s collection (figs. 1 and 7), and in the Museum of Practical 
Geology (fig. 9). 
Distribution.—Cenomanian (Beds 10 and 11), near Beer Head, Dunscombe, and 
Pinhay Cliff. 
TRIGONIA CRENULATA, Lamarck, 1819. Plate XIX, fie. 14. 
1819. Trigonia crenutata, Lamarck. Anim. sans vert., vol. vi, p. 63. 
1828. = = Defrance. Dict. Sciences nat., vol. lv, p. 294. 
«Foss. Aptien de la Perte du Rhone” (‘ Matér, Pal. Suisse,’ ser. 1, 1857), pl. sail, fig. 1. 
