272 



CRETACEOUS LAMELLIBRANCHIA. 



diculai- to tlie plane of the valves; height greater than length. Hinge-line equal 

 to a])out two-thirds of the height of the shell. Ventral margin very convex; 

 posterior margin forming an obtuse angle with the hinge-line. Umbones terminal, 

 curved inwards and forwards, the left umbo larger and more prominent than the 

 right. Surface smooth, except for growth-rings. 



Affinities. — /. tennis resembles 7. roncentricus, but the left umbo is less 



Fio. SI.— Inocerumns tenuis, Mantcll. Chalk Marl, Hamsey. Tlio typo. No. 5SUU, BrUisli iMiiscum (Nat. 

 Hist.). The specimen is sumewliat c-niiipiessod from front to back. Left valve and anterior view of both 

 valves. Kiijht valve shown in the next fiijure. 



prominent, the length of the shell is relatively greater, and tlie concentric rings 

 are less prominent. 



The fragmentary specimens described by Seeley as I'mtu lisaa a[)pear to belong 

 to this species.' 



Ti/i,cs.—Jn the Britisli Museum (No. 589(») from the Chalk .Marl of Hamsey. 

 A fragment, from the Red Limestone of Hunstanton, which appears to l)e one of 



^ Tlie form from tlie Kcd Limestone of Hunstaiiton wLieli wa.s named Fcniii Ininnrffsa bv Seeley 

 is at present known only liy an imjiorfeel left valve. It is perhaps allied to /. (ftmis, but is remark- 

 able in beiny mueli lonijei' than IiIl;!). The ty|ie is m the Sedgwick Mu.seiiiii, Canibriilge. Seeley, 

 'Auu. Mag. Nat. Hist.,' .ser. ,!, vol. .wii (Ib'OG), p. 1711. 



