THE CORALLIAN ROCKS OF ENGLAND. 399 



Avicula Struckmanni, De Loriol. PL XVI. fig. 3. 



This is a near ally of the last. 



The axis is a uniform elliptic curve, causing the ventral margin 

 to sweep round like the blade of a scymitar. The wing is broad, 

 and joins the shell by an impressed angle. This might be supposed 

 to be a Gervillia ; but there are no pits on the hinge-line, which, 

 however, is rather solid, even for an Avicula. 



In the Trigonia-beds, Weymouth. 



Avicula l^vis, spec. nov. PL XVI. fig. 2. 



The axis of the shell makes an angle of nearly 90° with the hinge at 

 first, but bends back slightly at a later stage ; convexity slight except 

 at the umbo, which rises uniformly from the surface ; hinge-line 

 very short, wing obsolete ; surface of shell smooth. 



In the Hambleton Oolite, Kepwick, and in the uppermost bed of 

 Lower Calcareous Grit in the Oxfordshire district. 



Avicula ovalis, Phil., var. obliqtja. PL XIV. fig. 13. 



A small and very oblique variety of this well-known shell. It is 

 remarkable for the beauty of its ornament and its general difference 

 of appearance from the type. A specimen from Cumnor seems to 

 possess a hinge of peculiar character. Occurs in tolerable abundance 

 in the Upper Calcareous Grit of Pickering. 



Lima l^viusctjla, Sowerby. 



There are certainly three forms which as much deserve separation 

 as the corresponding ribbed species ; and they come from very different 

 horizons : — (1) A roughly ribbed, somewhat orbicular shell, occurring 

 towards the base of the Lower Limestones in Yorkshire ; (2) Sowerby's 

 typical form, in the Coralline Oolite generally throughout England ; 

 (3) a very smooth transverse shell, frequently attaining large dimen- 

 sions, extremely characteristic of the Rag of Grimston. 



Pecten intertexttjs, Eb'mer. PL XV. fig. 9. 



This has long been known in Yorkshire as P. cancellatus of Bean, 

 but has never been figured from English specimens, as it 

 strangely escaped the notice of Professor Phillips, though magni- 

 ficent specimens of it, 6 in. in diameter, are preserved in the York 

 Museum. In England it occurs in the Coralline Oolite of the Malton 

 district, and of comparatively small size in the Trigonia-he&s of 

 Abbotsbury and Broad wey. 



Pecten qttalicosta, Etallon. PL XV. figs. 4, 4 a. 



"We for some time called this P. v avians, Rbmer ; but as it 

 appears doubtful what that species really is, and as Etallon's name 

 so admirably describes its characters, we have adopted it. The shell 

 is very characteristic of the Osmington Oolites and beds on a similar 

 horizon, but passes up into the false-bedded Limestones of Calne. 

 Each rib (and they are not regular) is crossed by a number of scaly 

 risings ; and those in the left valve in this species obscure the ribs. 



