162 CRETACEOUS LAMELLIBRANCHIA. 



and the Chalk Marl of Chard. The specimens seen are not sufficiently perfect for 

 fiffurinaf. 



M. rotundata is the type of the genus Mutiella. In France this species is found 

 in the Cenomanian of Le Mans, Sarthe, Rouen, etc. 1 



Family— UNICARDIIDiE, Fisch 



'.tier 



<iru us— Unicardium, A. d'Orbigny, 1849. 

 ('Prodr. de Pal.,' vol. i, p. 218.) 



Unicardium claxbiense, sp. nov. Plate XXV, figs. 7 «, b. 



Description. — Shell large, oval, inflated, with somewhat flattened sides, very 

 inequilateral ; anterior part much longer than posterior part. Anterior margin 

 well rounded, passing gradually into the antero-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 umbones the shell is 

 depressed. 



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

 centric ribs separated by relatively broad, concave interspaces. 



Measurements .• 



(1) (2) 



Length . 52 40 mm. 



Height . . 45 . 34 „ 



(1, 2) Benniworth Haven. 



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

 of the shell is longer than in U. heteroclitum (d'Orbigny) 2 ; also the ribs appear to 

 be narrow and sharper. 



Type. — In the Sedgwick Museum, Cambridge. 



Distribution. — Claxby Ironstone (zone of Belemniles lateralis) of Benniworth 

 Haven, Lincolnshire. 



1 Corbis? Morisoni, Woods, from the Chalk Rock of Cuckhamsley, is at present known l>y two 

 imperfect valves only. The hiuge cannot be seen, and the generic position of the species is still 

 uncertain. See Woods, ' Quart. Journ. G-eol. Soc.,' vol. liii, p. 392, pi. xxviii, figs. 13, 14. 



2 In Murchison, de Verneuil and de Keyserling, ' Gri'ol. Russie de l'Europe,' vol. ii (1845), p. 400, 

 pi. xxxix, figs. 9, 10. D'Orbigny, ' Prodr. de Pal.,' vol. i (1841)), p. 307. Eichwald, ' Letlmea Rossica,' 

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

 Mr. Lamplugh's collection. 



