8^ CRETACEOUS LAMELLIBRANCHlA. 



TlUiiONlA SCABKICOLA, LlJCCtt, 1875. 



1875. Lycetf, p. 130, pi. xxvii, figs. 4, 5. 



Ui'Duirls. — This form is very closely connected with T. caudata from the Lower 

 Grcensand — indeed, some specimens appear to be almost inseparable from that 

 species; but the majority of the Upper Grreensand examples have rather more 

 nmnerous and closer ribs towards the umbo, the shell less produced posteriorly, 

 and its height somewhat greater in proportion. It should, hoAvever, be noted 

 that a specimen from the Aptian of the Perte-du-Rlione, figured by Pictet and 

 Renevier,^ agrees perfectly with examples of T. scahricola from Blackdown and 

 Haldon. 



Types. — From Blackdown, in the Museum of Practical Geology. 



Distribution. — Greensand of Blackdown, Haldon, and Devizes. 



TrIGONIA CEENULIFERA, Lijcett, 1877. 



1877. Lycdt, p. 189, pi. xl, figs. 1, 7, 9. 



1896. A. J. JiiJces-Brotvne and W. Hill. Quart. Jouru. Geol. Soc, vol. lii, p. 154. 



Remarks. — The more prominent and fewer costse, and the greater slope of the 

 area and escutcheon, which Lycett regarded as features distinguishing this from 

 T. crenulatd, d'Orbigny, vary considerably in different specimens, as may be seen 

 by comparing Lycett's figures 1 and 9. In one example of T. crenuhta in the 

 British Museum, from Le Mans, the costge are actually fewer than in a form of 

 T. crennlifera of the same size. The costellse on the area, however, seem to 

 separate T. crenulifera from T. creniilata ; in the latter they appear to be found 

 only near the anterior end of the area. 



Types. — In Mr. Mej'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. 



TiuGONiA UEENULATA, LamarcJc, 1819. Plate XIX, fig. 14. 



1819. Tkigonia ceenulata, Lamarck. Anim. saus vert., vol. vi, ji. 63. 

 1828. — — Defrance. Diet. Sciences nat., vol. Iv, j>. 294. 



1 " Foss. Aptieu de la Perte du Elioiie" (' Mater. Pal. Suisse,' ser. 1, 1857), pi. xiii, fig. 1. 



