VA rRETACEOrS T.A:\rELTJBRAXrHTA. 



anteriorly. Ridges extend from the iinil)o to tlie angles at the margin of the 

 valve; the parts between tlie ridges are flattened. Lnnule Inrge, ovate, divided 

 into ail inner and an outer part l\y a ridge. Escutcheon wry large, consisting of 

 a median lanceolate part which is much depressed and sejiarated by a sharp edge 

 from a large concave outer portion. 



Ornamentation consists of broad concentric ridges which run parallel to the 

 margin of the valve and end abrupt!)^ at the hnude and escutcheon. Ver}- fine, 

 sometimes indistinct, ribs occur on the ridges and interspaces. 



Affinities. — Lucina sruljjfn is quite unlike any other Cretaceous species. Its 

 angular outline and large concave escutcheon give it an unusual appearance. 

 Externally it shows some resemblance to some species of Thi/nsirfiy^ but the hinge 

 and adductor impressions are at present unknown. Stoliczka regarded it as 

 probably a true Lucina. 



Jtemarlcs. — I have seen only four specimens, of which three are in the British 

 Museum and one is in the Museum of Practical Geology. 



Tijitc. — The type cannot be found. It is stated to lia\e come from the Speeton 

 Clay (Pzone of nch'ninites minimus). 



Pisfrihniion. — Lower Gault (Bed vi) of Folkestone. 



Lucina tenera (Smrrrhi), 1S8G. Plate XXIV, figs. 10—14. 



1836. Venus ? tenera, /. de C. Sowerhi/. Trans. Gcol. Soc, ser. 2, vol. iv, pp. lit, 



335, pi. xi, fig. 7. 

 1854. — — J. Morru. Cat. Brit. Foss., ed. 2, p. 231. 



1865. — — (? Lucina), F. J. Pictei and G. Campiche. Foss. Terr. 



Crt't. St^. Croix (Mati'r. 



Pal.Suisse,ser.4).p.l8P. 



1870. — — (PCabtatis), F. ,S7o/.iV2/w. Palwont. lu.lica, Cret. Fauna 



S. In.lia, vol. iii, p. 160. 

 1875. Lucina — A. J.JuJces-Brovme. Quart. Jouni. Geol. Soc, vol. xxxi. p. 



300, pi. XV, figs. 10—12. 



Description. — Shell oval, moderately convex, longer than liigh, inequilateral, 

 the anterior part longer and higher than the postei-ior part. Anterior margin 

 regularly rounded, passing gradually into the cui'ved ventral margin. Posterior 

 margin somewhat truncated, forming an obtuse angle with the postero-doi'sal 

 margin. Uml)ones of moderate size with a slight forward curvature. Lnnule 

 elongate, depressed, limited by a carina. Escutcheon large, not distinctly limited. 



1 Axinvs, Sowerln- ; Cri/ptoihin. T\\r\i'n. 



