96 ALBIAN FOSSILS DISCOVERED AT OKEFORD FITZPAIN'E. 



TRIGONIA ARCHIACIANA, Orbigny. 

 PI. iii., fig. 16. 



Trigonia Archiaciana, Orbigny : Paleontologie Francaise, 

 Cretaces Terrains, Lamellibranchia, 1843, PI. 290, figs. 6-10, p. 142. 

 Pictet and Roux : Desc. Moll. Foss. Gres Verts Geneve, 1853, PI. 

 35, fig. 4, p. 453. Pictet and Renevier : (Pal. Suisse) Desc. Foss. 

 Aptien, Perte du Rhone, and St. Croix, 1857, PI. 12, fig. 3, 

 p. 95. 



A single right valve of this shell is represented in the collection. 

 It is of oblong shape, feebly keeled and truncated posteriorly ; 

 ornamented with obtuse and transverse pallial ribs, which curve 

 obliquely and downwards, then meet at an angle on the carinal 

 margin, a corresponding series of arched costse covering the posterior 

 area; between the ribs aro closely arranged perpendicular plica- 

 tions, though only obscurely seen in our specimen on account of 

 bad preservation. 



Dimensions Height =21 ) , 



T ,, ~ > Millimetres. 

 Length = 2o | 



Lycett's T. Vicaryana is closely allied to this species, but 

 appears to differ in its greater number of pallial costse. 



RANGE OF SPECIES. Aptian to Albian. 



LOCALITIES. Lac de Joux, Perte du Rhone, Meuse, Ardennes, 

 Aube, and Yonne. 



TRIGONIA FITTONI (Deshayes), Leymerie. 

 PI. iii., fig. 15. 



Trigonia Fittoni, Leymerie : Me'm. Soc. Geol., France, 1842, 

 Vol. 5, PI. 9, fig. 6, p. 7. Orb-gny : Paleontologie Frangaise, 

 Terrains Cretaces, Lamellibranchia, 1894, PI. 290, figs. 1-5, p. 140. 

 Lycett : Monograph Paleontographical Society, 1874, PI. 23, figs. 

 4-5, p. 132. 



This species is represented by two small valves, which, although 

 somewhat fragmentary, exhibit the typical sculpturing. The 

 shell is ovately oblong, anterior side short with an elliptically 

 curved margin ; posterior end truncated ; surface with rather 



