46 MOLLUSCA FROM THE GREAT OOLITE. 



tenuissimis crebris, costulis poslicis majoribus subnodosis ; lineis increment! paucis 

 distantibus. 



Shell subrhoniboidal, umbones compressed, placed anterior to the middle of the valves, 

 and contiguous ; area narrow ; anterior portion with the margin rounded, posterior side 

 more lengthened, with an angle passing obliquely from the uinbones to the infero- 

 posterior extremity ; radiating costae very fine and closely arranged, the costae posterior to 

 the angle are larger and nodose ; lines of growth few and distant. 



The usual figure is compressed, and the posterior angle is acute, but there is much 

 variation in the convexity of the valves. The Area funicuhsa, Goldfuss, tab. 121, fig. 13, 

 has a general resemblance to it, but differs in having regular distinct concentric lines. 



It is the most common Area in the Great Oolite, and occurs throughout all the shelly 

 beds. 



Height, S hues ; length, 1 5 lines ; diameter through both the valves, 6 lines. 



Localities. Minchinhampton, in the Great Oolite ; Ancliff, Wiltshire. Leckhampton 

 Hill near Cheltenham, in the shelly free stone of the Inferior Oohte ; also in the Oolite 

 of Ponton, Lincolnshire. 



This species is dedicated to S. P. Pratt, Esq., F.R.S. 



Arca Eudesii. Tab. V, fig. 6, 6 a. 



Testa oblongd, subcompressd ; umbonibus obliquis, acutis, antemedianis distantibus, area 

 lata ; latere antico margine rotundo ; latere postico producto carinato longitudinaliter pli- 

 cate, plicis 3 latisprofiindis; dorso costulis radiantibus crebris incequalibus nodosis ; striis 

 concentricis frequenter obsoletis ; basi recta. 



Shell oblong, rather compressed, umbones oblique, acute, anterior to the middle of the 

 valves, and distant ; area large ; anterior side with the margin rounded, posterior side 

 with an obtuse carina more produced, and having upon the surface posterior to the carina 

 three large strongly-marked longitudinal phcations ; the dorsal surface has very fine 

 radiating costas densely arranged, knotted, and unequal ; concentric striae very faintly 

 traced ; inferior margin straight. 



The less convex form will distinguish it from Arca trisulcata, Goldfuss, the figure is 

 nearly that of his Arca fracta, but that shell is destitute of the posterior longitudinal 

 plications, it is scarcely so wide as Arca lata, Dunker, and more compressed upon the 

 dorsal surface ; that species would likewise seem to want the large posterior folds. It 

 occurs very rarely in the shelly beds of the Great Oolite. 



Height, 7 lines ; length 14 lines ; diameter through both the valves, 7 lines. 



Localities. Minchinhampton Common ; Langrune, Normandy. 



This species is dedicated to Professor Eudes Deslongchamps, of Caen, who has 

 obligingly forwarded to us, for comparison, many interesting shells from the Great Oolite 

 of Normandy. 



