114 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



folds of growth upon the sides of the valves are also remarkably, conspicuous, rendering 

 the surface rugose, and the basal sinuation is very strongly defined; in some of the more 

 aberrant forms the posterior side is so much shortened that the umbones are nearly 

 mesial ; they are then much elevated, and an oblique keel descends to the in fero- posterior 

 extremity. Our illustration faithfully represents this variety, numerous specimens of 

 which have been placed at our disposal by the kindness of Mr. Walton. 



Cardium globosum, Bean. Tab. XXXVIII, figs. 2, 2 a, 2 h. 



Cakdium GLOJiOSUM, Bean, in Mag. of Nat. Hist., 1839, p. 60, fig. 18. 



Testa suhorhiculari, <pquilafera, convexa, marginihus ellipticis curvatis ; superjicie striis 

 concentricis, tenuissimis, crebris instructis. 



Shell suborbicular, equilateral, convex ; the umbones moderately produced, acuminated, 

 and incurved ; the margins of the valves are elliptically curved ; the surface has very deli- 

 cate, regular, closely arranged, concentric striations. 



The length and breadth are equal ; the diameter through the valves is two fifths less. 

 Our illustration is taken from the original specimen figured by Mr. Bean ; its outline 

 should be somewhat more orbicular. The striated surface readily distinguishes it from 

 Cardium cognatum, Phil., which in other respects it resembles. 



Geological Position and Locality. The Cornbrash of Scarborough ; in the collection 

 of Mr. Leckenby. 



LiTHODOMUS PoRTERi, Lyc Tab. XL, fig. 29. 



Testa parva ovato-oblonga, convexa, angusta, umbonibus obliquis, suhterminalibus ; 

 margine anteriore recto, posteriore elliptico curvato, costis longitudinalibus numerosis, 

 tenuibus lineis concentricis decussatis. 



Shell small, ovately oblong, narrow, convex ; umbones oblique, subterminal ; anterior 

 border straight, its sides steep ; posterior margin curved elliptically ; longitudinal costae 

 numerous, delicate, closely arranged, sometimes bifurcating towards the lower border, and 

 decussated by closely arranged, concentric lines. 



The ornamentation is most prominent towards the middle of the valves, and is very 

 faintly traced upon the anterior side. It is allied to Lithodomus parasiticus, Desk, Mor., 

 and Lyc. (' Gr. Ool. Mon.,' "Biv.," p. 41, Tab. IV, fig. 19), but has greater convexity, 

 and is more narrow and cylindrical ; the numerous costae and decussating lines are also 

 distinctive features. 



Geological Position and Locality. Collected by W. Walton, Esq., in the Great Oolite 

 of Hampton Cliff's, near Bath. 



Dedicated to Henry Porter, Esq., M.D., who has investigated the geology in the 

 neighbourhood of Peterborough. 



