102 CRETACEOUS LAMBLLTBRANCHIA. 



RemarJrs. — Two incomplete specimens in Mr. Meyer's collection agree with M. 

 {Brachi/dontes) (rnera^^eri, fromtlie Cenomanian of Le Mans, except in having finer 

 ribs. Not having seen the type or other French specimens of M. Giifvantjeri I am 

 nnable to refer these examples definitely to that species. The ribbing on the 

 ventral snrface is clearly shown, and separates this form from M. divaricafa, 

 d'Orbigny.' 



A specimen from the Grreensand of Haldon, in Mr. Vicary's collection (pi. xvii, 

 fig. 4), agrees with M. Gnerangeri, especially with the example figured by 

 Gneranger, except in the absence of the fine ribbing on the ventral snrface ; this 

 difference may be due to imperfect preservation. The shell tapers more rapidly 

 toward the nmbones than in M. dlvaricata. 



Distribution. — Greensand of Haldon. Cenomanian (Meyer's Beds 10 and 12) 

 of Dunscombe. 



MoDioi.A (Beachydontes) vectiensts, sp. nov. Plate XVII, figs. 6 a, h, 7 a — c, 8. 



Deserij'fiuii. — Shell small, rather short, inflated, expanded, and compressed 

 posteriorly, extremities rounded. Ventral margin Avitli a sinus produced by a 

 mesial depression. Umbones obtuse, not terminal. Ornamentation consists of 

 many strong and somewhat irregular ribs, which cover the entire surface and 

 generally bifurcate toward the margin of the valve. 



Measurements : 



(1) 



{■^) 



(3) 



(4) 



(5) 



14 



14 



13-5 



12-5 



9 mm. 



7-5 



8 



8 



8 



i> » 



Length .... 

 Height .... 

 Thickness . . . .6 — — — — ,, 

 (1), (5) from the Crackers, Atherfield. 



(2) from the Perwa-bed, Eedcliff. 



(3) from the Atherfield Beds, Littleton Pit, near Guildford. 



(4) from the Atherfield Beds, East Shalford. 



Affinities. — The smaller forms of this species resemble M. striato-co.'^tnta 

 (d'Orbigny), but possess stronger and less regular ribs, and are without the con- 

 centric ribs. 



M. iiiorinicus' (de Loriol) is also similar, but has more regular rilxs, which do not 

 bifurcate, and some parts of the shell are without ribs. 



1 'Pal. rran9. Terr. Cre't.,' vol. iii (1844), p. 275, pi. cccxl, figs. 3, 4; ' Prodr. de Pal.,' vol. ii 

 (1850), p. 246; Pictet and Campiche, ' Foss. Terr. Cret. Ste. Croix' (1867), p. 511. 



' De Loriol and Pellat, ' Portlandien de Boiilogne-sur-Mer ' (' Mem. Soc. Phy.s. et d'Hist. Nal. de 

 Geneve,' vol. xix, 1866), p. 91, pi. ix, fig. 4. 



