196 Mr. K. H. Newton on Fossil MvUukCJ. (be. 



liowevcr, quite distinct, and they do not appear to have had 

 ])ioduced terminals to the cardinal region. 



Area cf. lactea, Linna^u?. (PI. VI. figs. 2, 3.) 



Jroa lactea, Linnaeus, Syst. Naturae, 1758, ed. x. p. 694 ; Searles "Wood, 

 Mon. Pal. Soc. (Crag'Mollusca) 1850, pi. x. fig. 2, p. 77. 



Fossularca lactea, Sacco, Moll. Terziarii Piemoute «S:c., 1898, vol. ixvi. 

 pi. iii. tjg3. 20-1^3, p. 19. 



Remarks. — The two examples regarded as being closely 

 allied to the Mediterranean species lactea are of very similar 

 dimensions to that form, the length being about one and a 

 half times the height. The sculpture, which also agrees, 

 exhibits a series of fine and ch:)sely arranged costae crossed by 

 equidistant concentric growth-lines. The valves, however, 

 are rather compressed than otherwise, which would l)e the 

 chief reason for not regarding tiiem as belonging to the true 

 lactea. They differ from Area nigeriensis, next described, 

 in their less angulate contour and more median umbones. 



Dtmenst'oyif (largest example). — Length =14:, height = 

 9 mm. 



The Linnajan shell has been determined from the Pliocene 

 (Coralline and Hed Crags) leds of England, whilst Sacco 

 has recognized it under Fossularr.a of Cossmann, and considers 

 it as occurring in Italy in rocks ranging from Miocene 

 (Helvetian) to Pliocene (Astian) times. 



Area nigeriensis, sp. n. (PI. VI. figs. 4, 5.) 

 Description. — Shell small, inequilateral, oblong, length 

 nearly twice that of the height; anterior margin rounded, 

 ]»osterior truncated, slightly excavated; stride equal, nume- 

 rous and fine (about 60), crossed by concentric growth-lines; 

 valves depressed ventrally. 



Dimensions (largest specimen). — Length=:17, height = 

 9 mm. 



Remarks. — This form is distinct from Area tetragona of 

 Poll, found in the Mediterranean and in the Pliocene deposit.-? 

 of Europe, by reason of its more equal striations and (he less 

 elevated nnibonal region. The radial costae ornamenting 

 the ]>osti'rior .surface of ^1. tetraxjona are much stronger and 

 fewer than those of the present form ; both species, howevei-, 

 are siuiilar in possessing a horizontal hinge-line which is 

 ])aiall'd with the veiitral margin. 



Cardhim cf. deeorticdum, S. V. Wood. (PI. VI. figs. 6, 7.) 



Cardtirm dccorticatum, S. V. Wood, Mon. Pal. Soc. (Crag MoUusca) 

 lb53, pi. xiv. tig. 1 d, p. 159. 



Description. — Shell cordately ovate, slightly oblique. 



