132 MOLLUSCA FROM THE GREAT OOLITE. 



Mytilus (Modiola) ungulatus. Tab. IV, fig. 5 (M. tumidus). 



M. ungulata, Young and Bird. Geol. Yorksh., pi. 7, f. 10. 

 M. tumidus, antea, p. 37, pi. iv, f. 5. 



This species has been previously figured under the name of M. tumidus, p. 37, but it is 

 not distinct from the Yorkshire shell, and the latter name cannot therefore be retained. 



Cuculljsa cancellata, Phil. Tab. XIV, fig. 12. 



Cucull^a cancellata, Phil. Geol. York., 1, t. 9, f. 24, t. 11, f. 44. 

 — obliqua, Lycett. Ann. and Mag. Nat. Hist., 1850. 



Testa ovato-rhomboided perobliqud ; umbonibus antemedianis confirms, latere antico brevi, 

 latere postico fornicato oblique declivi et producto ; superficie lineis radiantibus minutis 

 crebris aliis concentricis decussatis. 



Shell ovately rhomboidal, very oblique ; umbones placed near to the anterior extremity 

 of the hinge line, and contiguous ; anterior side short, its margin rounded, posterior side 

 with an oblique ridge, obtuse, and much elongated posteriorly ; the surface with very 

 densely arranged, equal, regular, radiating lines, decussated by others concentric and 

 equally densely arranged ; the lines are smooth, and the angles produced by the junction 

 of the decussating lines have a punctated appearance ; upon the anterior side of the shell 

 the radiating lines are rather less densely arranged. 



The surface of this species has a considerable resemblance to Cuculleea cucullata, 

 Goldfuss, but the latter shell is more convex and is less elongated, the area being likewise 

 larger. 



Geological position and localities. — At Scarborough, in the hard grey limestone of 

 the Great Oolite; in Gloucestershire, it occurs in the middle division of the Inferior 

 Oolite. 



Unicardium gibbosum. Tab. XIV, fig. 11. 



Testa ovato subglobosd ; umbonibus magnis medianis, curvatis ; margine cardinali brevi, 

 subrecto, et subhorizontali ; marginibus aliis curvatis ; superficie plicis magnis irregularibus 

 et inaqualibus. 



Shell ovately sub-globose ; umbones large, mesial, prominent, and curved forwards ; 

 hinge margin short, nearly straight, and horizontal, its posterior extremity rather angulated, 

 the other margins of the valves regularly rounded ; the surface is covered with large, 

 irregular, and unequal concentric plications ; the thickness of the test is moderate. 



The umbones are more nearly mesial than U. depressum and TI. impressum ; they also 

 project more, and therefore more nearly resemble U. varicosum, but the anterior side is 



