LIMA. 17 



ornamented with numerous pits having a regular radial and concentric arrange- 

 ment and giving rise (in some cases) to the appearance of slightly-raised radial 

 and concentric ribs. Near the ventral margin the pits become more elongated 

 (parallel with the margin) and their concentric arrangement may become wavy or 

 irregular. At the anterior and posterior margins the radial arrangement is often 

 more distinct than elsewhere. Sometimes on the median part of the valve the 

 concentric arrangement alone can be recognised. 

 Measurements : 



(1) (2) (3) (4) (5) (6) (7) (8) 



Length . 31 . 27 . 25 . 24 . 22 . 20 . 18 . 12 mm. 

 Height . 25 . 23 . 21 . 21 . 19 . 17 . 16 . 10 

 (13, 5, 7, 8) Totternhoe Stone, Burwell. 

 (4) Chalk Marl, Ventnor. 

 (6) Clevancy. 



Affinities. This species closely resembles Lima albensis, d'Orbigny, 1 from the 

 Gault of Ervy (Aube), Macheromeml (Ardennes), the Perte-du-Rhone, etc. I have 

 not seen any specimens of L. albensis, but it appears to differ from L. globosa in the 

 absence of the punctate ornamentation and in having a smaller apical angle. 



L. globosa is distinguished from L. Hoperi (see below) by its smaller size, more 

 inflated valves, and by the close-set rows of radial and concentric pits. 



Type. In the Museum of the Geological Society, No. 1538, from the Chloritic 

 Marl of the Isle of Wight. 



Distribution. Gault of Folkestone. Red Limestone of Hunstanton. Upper 

 Greensand of "Warminster. Cambridge Greensand (base of Chalk Marl). Chalk 

 Marl of Ventnor, Clevancy, Chilcomb well (Winchester), Burham, Folkestone and 

 Cherry Hinton. Cenomanian of Wilmington. Totternhoe Stone of Burwell. 

 Zone of H. subglobosus of Chilcomb and Fulbourn. 



LIMA (PLAGIOSTOMA) HOPERI, Mantell, 1822. Plate IV, figs. 7, 8a, b, 9, b, 10, 



lla, b, 12a, b. 



1822. PLAGIOSTOMA HOPERI, G. MantelL Foss. S. Downs, p. 204, pi. xxvi, 



figs. 2, 3, 15. 



J. de C. Sowerby. Min. Conch., vol. iv, p. Ill, 

 pi. ccclxxx. 



1 ' Pal. Fran9. Terr. Oct.,' vol. iii (1847), p. 541, pi. ccccxvi, figs. 15, 16 ; 'Prodr. de Paleont.,' 

 vol. ii (1850), p. 138 ; Pictet and Eoux, ' Moll. Foss. Gres verts de Geneve ' (1852), p. 488, pi. xl, 

 fig. 9; Pictet and Campiche, "Foss. Terr. Cret. Ste. Croix " ('Mater. Pal. Suisse,' ser. 5, 1869), 

 p. 160. 



3 



