LUCINA. 1 



J-) 



Ornamentation consists of numerous, regular, strong, concentric ribs which become 

 smaller near the antcro-dorsal and postcro-dorsal niai-gins. 

 Measurements : 



(2) (3) . 



1-i . lo . iz-o . \i inin. 



12 . 11 . 



7 . G-5 . 



(1—5) Gault, Folkestone. 



Aj)inities. — In form and ornamentation this species resembles Jj. Sanctai-Crucu, 

 Pictet and Campiche,' but is much smaller and relatively longer. 



Tijpc. — The tj-pe came from the (Jault of Folkestone, but cannot now be 

 found. The specimens figured by Jukes-Browne are in the Setigwick Museum, 

 Cambridge. 



Distriljiiflua. — Gault of Folkestone and Black Ven. Cambridifc Greeusand. 

 Upper Greensand (zone of Scldeciibachia rostrata) of Devizes. 



LuciXA DoWNESr, sp. nov. Plate XXIV, figs. 15 «. — r. 



Description. — Shell oval or nearly orbicular, moderately convex, slightly iiieijui- 

 lateral, longer than high, postero-dorsal part compressed. Anterior and ventral 

 margins rounded. Posterior margin less convex than the anterior, forming an 

 obtuse angle with the convex postero-doi-sal margin. Umbones of moderate size. 

 Lunule elongate. Ornamentation consists of numerous regular, coucentrie, lamellar 

 ribs separated by broad, flat interspaces with fine concentric ribs. 



Measurements : 



(1) (2) 



Length . 32 . 20 mm. 



Height . 28-5 . 24 „ 



Thickness . 14 — ,, 



(1, 2) Blackd.iwii. 



AlJiuillrs. — This species resembles L. ('iiniiirli,nui., d'Orbigny,' \'ix>n\ the 

 Neocomiaii, Imt the undjones are less prominent and the shell is less iiRMHiilateral. 

 It is also similar to L. submimismalis, d'Orbigny,'^ from the Aachen Greensand, 

 l)ut the ribs are more numerous and the antero-dorsal margin has a greater 



' " Terr. Crt't. Ste. Croix" (' Mater. Pal. Suisse," ser. -4, 18tJG). p. 28;t, pi. cxxii, fig. 8. 



2 ' Pal. Fi-au9. Terr. Crct.,' vol. iii (1844), p. 110, pi. cclxxxi, figs. 3—5. 



•* Holzapfel. " Die MoUusk. Aacheu. KreiJe " (' PalsEoutographica,' vol. xxxv, 1880), p. 187. 

 pi. xix. figs. 1—3. Eavn, ' Mollusk. i Daumarks Kridtafl. I. Lamellil.r.' (PJ02), p. 12!i, [.l. iv. 

 tiu'. 21. 



