REV. J. E. CROSS ON THE GEOLOGY OF N.W. LINCOLNSHIRE. 127 



Tancredia perrea (Cross, MS.), Ether. PI. V. fig. 4. 



Shell ovately trigonal, donaciform, elongated, acutely pointed at the 

 anterior extremity ; nmbones small, depressed and slightly incurved ; 

 posterior side, gaping extremity acute and incurved ; postero- 

 dorsal edge slightly convex, and having a depressed concave space or 

 band, bounded by angular sides or ridges proceeding from the umbo 

 to the acute extremity, edge reflected inwards or infolded ; antero- 

 dorsal edge straight, with a groove along the hinge-margin, which 

 proceeds from the umbo nearly to the anterior end, edge or margin 

 also infolded ; ventral margin convex or elliptically rounded ; hinge 

 complicated, lateral tooth large, posterior, and approximate ; lateral 

 tooth of left valve projecting ; anterior tooth small and under the 

 umbo, lines of growth faint or indistinct, shell smooth, no ornamen- 

 tation ; neither muscular scars nor pallial impressions visible in our 

 specimens. 



Affinities. — This shell closely resembles Hettangia (Tancredia) 

 ovata, Terq. and Piette, Mem. Soc. Geol. Prance, " Lias inferieur de 

 Test de la Prance," t. 6, f. 8, 19, also figured by Chapuis & Dewal- 

 que, Mem. de l'Acad. de Brux. t. xxv., " Poss. Terr. Jurass." p. 173, 

 t. 25. f. 2. Our shell, however, is less deltoid in form, being more 

 elongated, and the anterior extremity much more acute ; it differs 

 from Hettangia broliensis, Buv., Pal. Dept. de la Meuse, p. 14, 1. 10. 

 f. 22, 23. 



Loc. Scunthorpe. Formation. Lower Lias (Ironstone series.) 



Tancredia liassica (Cross, MS.), Ether. PI. Y. figs. 5, 5 a. 



Shell donaciform, elongated, slightly rounded or subacute at 

 the anterior end, which is broad and ventricose; antero-dorsal edge 

 or slope straight and angular ; the depressed area or space extend- 

 ing from the umbo to extreme anterior end is narrow; the inner 

 edge of this area is rounded, the outer very acute; posterior ex- 

 tremity elongated or attenuated ; umbones nearly central, slightly 

 incurved ; ventral margin or border rounded, and much the deepest 

 at the anterior side. 



This shell differs from T. ferrea in its greater depth and obtuse- 

 ness anteriorly ; it is also more attenuated posteriorly, and the teeth 

 are smaller in proportion to the size of the shell than in T. ferrea. 

 The anterior extremity of T. ferrea is acutely pointed, in T. liassica 

 rounded or obtuse. I cannot refer it to any continental form ; both 

 this and T. ferrea are quite distinct from any known species. 



Loc. Sheffield Hill. Formation. Lower Lias (Pecten-bed). 



Pam. CYPKINIILE. 

 Hippopodium, Sowerby, 1819. 



This remarkable genus occurs only in the Lias, the type H. pon- 

 derosum being somewhat abundant in the upper part of the Lower 

 Lias, associated with Ammonites raricostatus, Zieten, A. armatus, 

 Sow., and Thecoeyathus rugosus. This species comes from a lower 



