176 SUPPLEMENT TO THE BRITISH 



above named. According to Mr. Walford W. Lycetti occurs, likewise, in the Upper 

 Lias of Byfield, in Northamptonshire. 



Waldheimia Lycetti varies a good deal in shape as well as in dimensions. The largest 

 specimen I was able to examine measured-length 9, breadth 9, depth 5 lines. It is often 

 somewhat marginally square, with rounded angles, the hinge-line being long ; the beak 

 small and perforated by a minute circular foramen. It varies likewise to a considerable 

 extent in the degree of convexity of its valves ; the ventral valve is always the deepest. 

 In some examples the valves seem almost uniformly convex without any fold or sinus, in 

 others the dorsal valve is nearly flat and front line straight, but in the larger number of 

 individuals there exists a median depression, commencing at about half the length of the 

 valve and extending to the front, while in a few, the reverse seems to be the case, for 

 there exists, in place of the concave depression, a slight elevation simulating a mesial fold. 

 The species is, however, easily recognisable in its various modifications and seems 

 characteristic of the deposit in which it occurs. 



159. Waldheimia Dorsetensis, Walker. Sup., PI. XXIV, figs. 6, 7, 8. 



Waldheimia Dorsetensis,/. F. Walker. Geol. Mag., New Ser., vol. iii p. 574, 1876. 



Shell somewhat sub-pentagonal, broadest posteriorly, tapering anteriorly, nearly 

 straight in front ; as broad as long or slightly longer than wide ; ventral valve much 

 deeper than the dorsal one and carinated along its middle ; beak large, very much 

 incurved, and truncated by a small circular foramen overlying the umbone of the opposite 

 valve. Dorsal valve slightly convex, sometimes a little depressed along the middle. 

 Surface of valves smooth and marked only by a few concentric lines of growth ; loop 

 long. Two specimens measured — 



Length 10, width 9, depth 6 lines. 

 8, " 8, " 5 lines. 



Obs. — Waldheimia Dorsetensis was found by Mr. J. F. Walker in great abundance 

 in the Supra-Coralline bed at Abbotsbury in Dorsetshire, associated with Wald. lampas, 

 Ter. subsella, and Bh. pinguis var. pectunculoides. The rock is of a red ferruginous colour, 

 of which the fossils partake. 



160. Waldheimia Margarita, Oppel. Sup., PL XXIV, figs. 12, 13. 



Terebratula (Wald.) Margarita, Oppel. Ueber die weissen und rothen Kalke von 



Vils in Tyrol ; Wurttemb. Naturw. 

 Jahreshefte, Jabrgang XVII, p. 35, 

 tab. ii, fig. 3, 1861. 



