I'i2 CRETACEOUS LAMELTJBRAXCTTTA. 



and the Cliulk Mini of Chard. The specimens seen are nut sulHciently perfect for 

 fiii^urinij. 



M. rotwudata is the type of the genus Matiella. In France this species is i'uiuid 

 in the Cenomauian of Le Mans, Sarthe, Rouen, etc.^ 



i'^amiVy— UNICARDIID.E, Fisrh <,: 



Genus — Unicaedium, .1. iTOrhhjuij, 18i*,). 

 (•rruilr. do Pill.,' vol. i, p. -218.) 



Unicakhhm ( laxciense, sp. nov. Plate XXV, figs. 7 a, l>. 



JJencriptiuii. — Sliell kxrge, oval, inflated, witli somewhat flattened sides, very 

 inefjuilateral ; anterior jjart much longer than posterior part. Anterior margin 

 WL']] rounded, passing gradually into the antei'O-dorsal margin, and into the ventral 

 margin, which is only slightly curved. Posterior margin truncated. Umbones 

 broad, curved inward and slightly forward. In front of the unil)ones the shell is 

 dej)ressed . 



Ornamentation consists of narrow, sharp, prominent, somewhat irregular con- 

 centric ribs separated by relatively broad, concave interspaces. 

 Measurements : 



(1) (a) 



Length . . 52 . 40 mm. 



Height . . 45 . 34 „ 



(1, 2) Bfuuiwortla Haveu. 



Affinities. — In this species the umbones are not so high ami the posterior part 

 of the shell is longer than in U. Iteterai'lifiim (d'Orbigny)- ; also the ril)s appear to 

 be narrow and sharper. 



Type. — In the Sedgwick Museum, Cambridge. 



Distrihntion. — Claxl)y Ironstone (zone of llclciiniitc.s lutrrnlis) of Benniworth 

 Haven, Lincolnshire. 



') 



' Corbis ? Morisoni, Woods, from the Chalk Rock of Cuckhamsley, is at present knowni by two 

 iiuperfoct valves only. The hiuge cannot l)e seen, and the generic position of the species is still 

 uucortain. See Woods, ' Quart. Journ. Geol. Soc.,' vol. liii, p. 392, pi. xxviii, figs. 13, 14. 



- In Murchison, de Verneuil and de Keyserliug, ' Gt'ol. Russie de I'Europe,' vol. ii (1845), p. 460, 

 pi. xxxix, figs, n, 10. D'Orhiguy, ' Prodr. de Pal.,' vol. i (1840). p. 367. Eichwald, ' Lethiea Rossica,' 

 vol. ii (1868), p. 647. Two examples of U. heteruclitum from the Lower Volgian, near Moscow, are in 

 Mr. Lamplugh's collection. 



