206 SUPPLEMENT TO THE BRITISH 



elsewhere. It is found also in the Bradford Clay at Tetbury-Road Station ; and in 

 the Cornbrash of Yaxley, near Peterborough ; where it is associated with Bh. Leedsii. 



204. Var. Yaxleyensts, Dav. Sup., PI. XXVII, fig. 23. 



This is an extreme and well-marked variety, or rather variation in shape, oiBh. concinna, 

 in which the frontal portions of the valves are very much thickened ; each valve, as it 

 approaches the serrated frontal margin, is more or less suddenly or abruptly bent at 

 nearly right angles, giving to the frontal view of the shell a broad, square, flattened 

 character. The ribs are also to some distance from their extremities grooved 

 along the middle, as is seen in Eh. octoplicata, Bh. Wilsoni, and many other species. 

 This shell does not appear to have much exceeded 9 lines in length by 10 in breadth and 

 7 in depth. It occurs in great abundance, along with typical examples of Bh. concinna, 

 in the Cornbrash at Yaxley, near Peterborough. It is associated with several varieties of 

 Wald. obovata, Ter. Bentleyi, and Bh. Leedsii. 



205. Rhynchonella stjb-concinna, Dav. Ool. Mon., p. 90, PI. XVII, fig. 17. 



This shell occurs in the upper portion of the Middle Lias (Zones of Am. margaritatm 

 and A. spinatus). Professor R. Tate quotes it in the ' Yorkshire Lias ' from the Zones of 

 Am. Jamesoni, at Huntcliff, Peak, and A. capricornvs, Huntcliff (?) Yorkshire. It is 

 still a question whether B.fodinatts, Tate, is specifically distinct from B. sub-concinna. 



206. Rhynchonella fomnalis, B. Tate. Sup., PI. XXVIII, figs. 39, 40, 41. 



Rhynchosella fodinalis, R. Tate. The Yorkshire Lias, p. 424, pi. xv, fig. 16, 



1867. 



Shell transversely oval or obovate, wider than long ; dorsal valve moderately convex, 

 deeper than the ventral one ; margin in front rising with a gentle undulation ; lateral 

 margins rounded ; fold of moderate elevation occupying less than a third of the breadth 

 of the anterior half of the valve ; beak in ventral valve acutely pointed, incurved, with a 

 small foramen situated under its acute termination and the hinge-line, from which it is 

 but little separated by its small deltoidial plates ; beak-ridges sharply defined, leaving 

 between them and the hinge-line a long, narrow, flattened space or false area. Sinus 



