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 ])art of the valve the 

 concentric arrangement alone can be recognised. 

 Measurements : 



(1) (2) (3) (i) (5) 



Lent^th . 31 . 27 . 25 . 24 . 22 



Height . 25 . 23 . 21 . 21 . 19 



(1—3, 5, 7, 8) Tottemhoe Stoue, Bunvell. 

 (4) Chalk Marl, Veutuor. 

 (6) ,, ,, Clevancy. 



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

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

 not seen any specimens of L. albent^ls, but it appears to differ from //. glfiljosa in the 

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



L. (jlohosa is distinguished from L. Hoperl (see below) by its smaller size, more 

 intiated 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 Ilunstaaiton. 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. Totternlioe Stone of Burwell. 

 Zone of H. subylobosus of Chilcomb and Fulbourn. 



Lima (Plagiostoma) lloi'uui, Mantell, 1822. Plate IV, figs. 7, Sa, l>, \hi, l>, 10, 



11((, /;, 12a, b. 



1822. Plagiostoma Hopeei, G. Mantell. Foss. S. Dowus, p. 20-i. pi. xxvi. 



figs. 2, 3. 15. 

 — _ — /. de €■ Sowerhij. Min. Couch., vol. iv, p. ill. 



pi. ccckxx. 



1 'Pal. Fran?. Terr. Crct.,' vol. iii (1847), p. 541, pi. cceexvi, figs. 1-5, IG ; ' Prodr. de Palcont.,' 

 vol. ii (1850), p. 138 ; Pictet aud Roux, ' Moll. Foss. Grcs verts de Geuivc ' (1852), p. 488, pi. xl, 

 tig. 9; Pictet aud Campiche, " Poss. Terr. Crct. Ste. Croix" (' Mat^'r. Pal. Suisse.' ser. 5. 18(3'.'). 



p. 160. 



o 



