6 CRETACEOUS LA:\IELLIBT{ANCHTA. 



nearly equal size, but sometimes (chiefly near the posterior l)or(l('r) with smaller 

 intercalated ribs. The ribs diverge slightly from a nearly median line, and bear 

 short spiny or scaly projections at regular intervals but not usually with a con- 

 centric arrangement. The spines are rather nearer the inner than the outer side 

 of each rib. The gi-ooves are narrow near the umbo but become broader in passing 

 ventrally, and at the ventral margin may exceed the ribs in breadth. The grooA-^es 

 are rounded and (in some specimens) show transverse ridges. More or less distinct 

 "•rowth-lines occur at intervals. 

 Mffis^urements : 



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



Length . 25 . 21 . 20 . 17 . 16 . It luni. 

 Height . U . 28 . 29 . 23 . 23 . 20 „ 

 (1,3) Cambridge Greensand. 



(2) Base of Chalk Marl, Folkestone. 

 (4, 5) Upper Greensand, Warminster. 

 (G) ,, „ Haldon. 



Affinities. — This species belongs to the same group as the Senonian forms L. 

 Dtnikcri, Hagenow,^ and L. muricafa, Goldfuss." It is distinguished from the 

 former by its smaller apical angle and by the spines on the ribs being placed more 

 closely together. L. muricata differs from L. suhovalis in ha\^ng fewer ribs with 

 their ornamentation developed into long scale-like projections, and in having 

 oblique grooves in the interspaces. 



Bcmarlcs. — A comparison of the type of Lima mhovalis with examples of L. 

 oriKitd leaves no doubt as to their identit)\ The type-specimen of the former is 

 somewhat worn, but sufficiently well-preserved for identification, and another 

 specimen on the same tablet shows the ornamentation quite clearly ; the shell is not 

 silicified, so that it was evidently not obtained from Blackdown — the locality given 

 by Fitton — but it has all the appearance of specimens found at AYarminstcr. 



The examples from the Candiridge Greensand were referred to L. UnuUmana, 

 d'Orbigny,' by Mr. Jukes-Browne. The interior of these is filled Avith phosphate, 

 and the shell, although in some respects well-preserved, is rather abraded, so that 

 the remains of the spines usually appear as notches on the inner side (that facing 

 the median line) of each rib. The transverse ornamentation in the grooves is often 

 very distinct. Mr. Jukes-Browne has recently re-exAmined these specimens and 

 agrees with mc in thinking that they cannot be separated from L. svhovaJis. I 



1 ' Neues Jahrl). fiir Miu., etc' (1842), p. 556; Vogel, 'Holliind. Krcide ' (1895), p. 17, pi. i, fiy. 9: 

 Ravn, 'Mollusk. Danmarks Kridtaflej.' (1902), p. 100, pi. ii. fig. 14. 



-' ' Petref. Germ.,' vol. ii (1836), p. 89, pi. ciii, fig. 4; Vogel, oj}. cit., p. 17, pi. i, figs. 10, 11. 



' ' Pal. Fran?. Terr. Cn't.,' vol. iii (1847), p. 542, pi. ccccxvii, figs. 5—8; ' Prodr. de Pal.' (1850), 

 vol. ii, p. 138; Pictet and Campiche, " Foss. Terr. Cn't. Ste. Croix" ('Mater. Pal. Suisse,' ser. 5, 

 1869), p. 154. pi. clxvi, fig. 2. 



