110 INVERTEBRATA. 



PECTUNCULUS MARULLENSIS, Lcymeric. 

 (Plate v., fig. 11.) 



Pectunculus Marullensis, Leym. 1842, Mm. Soc. Geol. France, 



v., pi. ix., f. 2. 



D'Orbigny, Terr. Crdt, p. 187, pi. 

 cccvi., f. 16. , 



The ribs vary ; they do not shew such a regular cross-line 

 structure as is shewn in M. D'Orbigny's figures. 



Localities. Upware, Shanklin. 



S. Europe. Paris basin, Middle Neocomian. 



PECTUNCULUS OBLIQUUS, sp. nov. 

 (Plate VI., fig. 1, a, b, c, d) 



Shell thick, ovate-oblong, transverse, slightly oblique ; convex, 

 but somewhat flattened in the centre ; surface marked with lines 

 of growth and ornamented with delicate radiating striae. 



Umbones contiguous, rather depressed, oblique, situated in 

 about the line of the anterior third of the shell. Hinge line short, 

 less than half the length of the shell. 



Ligament area narrow with several (about eight) angular 

 furrows. Hinge strong, furnished with few central transverse 

 teeth, and three longitudinal lateral teeth upon each side of the 

 semicircular hinge shelf. 



The surface striae are very numerous, gently convex, with 

 simple, narrow interspaces. 



The species is best distinguished by its shape, which is almost 

 cuneiform, and its anterior, oblique umbones. It approaches nearest 

 to some Jurassic species from the Great oolite and Coral rag. 



Measurements. Antero-posterior diameter, 16 mm. ; umbono- 

 pallial diameter, 13 mm. Thickness (through both valves), 

 10 mm. 



Locality. Upware. 



