128 INVERTEBRATA. 



MODIOLA ARCADIFORMIS, D. sp. 



(Plate vie, fig. 2, a, b.) 



Like the preceding this is a small boring shell found in the 

 phosphatic masses. 



Shell small, oblong, convex (^4rca-shaped) ; anterior side 

 rounded ; pallial border gently convex ; anal border square-truncate. 



The umbo is large, rather prominent, but flattened, incurved 

 and pointed ; it is well removed from the anterior end. A sharply- 

 angular keel runs from the umbo to the posterior pallial margin, 

 cutting off a distinct, concave posterior region. There is a strong 

 internal ligament ridge. 



' The surface is covered with distinct lines of growth, which are 

 sharply angulated over the keel. The species is well distinguished 

 by its area-like shape, the posterior keel and hollowed posterior 

 area. 



Localities. Upware, Potton. 



BRACHIOPODA. 



(See ante, p. 20.) 



Megerlia (Kingena) rhomboidalis, n. sp. 

 (Plate VII., fig. 3, a — a) 



Description. Shell rhomboidal, slightly longer than broad, 

 moderately convex, thickest near the beaks. Surface smooth or 

 marked with lines of growth. Shell structure coarsely punctate. 



Dorsal valve obtusely trigonal, convex, especially near the beak. 

 Hinge line gently curved ; front obtusely pointed. A distinct line 

 extending f the length of the shell indicates the internal dorsal 

 septum of the genus. 



Ventral valve rhomboidal, obtusely keeled from back to front. 

 Beak sharp ; beak-ridges acute, area elongated, flattened and 

 concave. 



Deltidium in two pieces ; foramen small. 



Measurements. Length, 9^ mm. ; breadth, 9 mm. ; thickness, 

 G mm. 





