FROM THE INFERIOR OOLITE. 533 



sible to speak with certainty. Certainly the larger figures of Ph. 

 ovulum, especially those of foreign authors, are very different from 

 the larger Dimdry forms, which seem to have well-defined charac- 

 teristics of their own. 



Pholadomya fortis, n. sp. ? Plate XIX. fig. 8. 



Shell moderately convex, ovate, rather flattened inferiorly. Um- 

 bones subcentral, direct, large, but low, and rather compressed. 

 Escutcheon long, bounded by a strong ridge. Front and rear 

 margins apparently convex ; inferior margin nearly straight. Sur- 

 face with irregular concentric marks, which are sharp and occasion- 

 ally prominent, and with eleven very distinct and distant linear 

 ribs reaching the margins and spreading over the whole shell. Test 

 very thick. 



Dimensions. Length 1J inch, width 2 inches, depth 1 inch. 



I should have been inclined to suppose these shells, of which I have 

 obtained two or three rather imperfect specimens from Dundry, to 

 be a variety of Ph. ovalis, Sow., were it not for the very great thick- 

 ness of their tests ; for although Sowerby supposes one of his shells 

 to have this quality, it is the one he obtained from the Portland- 

 beds, and which does not at all agree with the present shell in other 

 particulars. In the specimens of that species described by Morris 

 and Lycett, whose figures are more like the present shell than are 

 Sowerby's, the test appears to be of the usual thinness in this genus ; 

 and I have obtained other shells from Dundry agreeing with their 

 figure, and therefore, as I suppose, the true Ph. ovalis, Sow., which 

 are certainly distinct from the present species. 



It also bears great resemblance to Ph. tumida, Ag., which, with 

 other species, Mosch unites with PA. canaliculata, Eo. ; but I find no 

 mention of their having thick shells, and this, if it had been so, 

 would have been almost sure to be mentioned from its rarity in this 

 genus. It must therefore remain doubtful whether they belong to 

 this species. 



The name "Ph. angustata, Sow.," is aften found in lists and labels 

 of Inferior Oolite shells. I believe that this is because his figure 

 has the appearance of being foreshortened, and is therefore supposed 

 to be less transverse than is the fact. However, on examining his 

 original specimens, it is at once seen that they are accurately repre- 

 sented by his drawings. I do not think this form ever occurs in 

 the Lower Oolites, but that when the name is so used, it is applied 

 to lengthened specimens of Ph. ovalis. 



Pholadomya Newtonii, n. sp. Plate XIX. figs. 9, 9 a. 



Shell small, flatly convex, subtrigonal. Umbo anterior, small, 

 rather incurved. Anterior side large, swollen, and convex ; posterior 

 much attenuated, and flatter. Margins convex, especially the anterior 

 one. Escutcheon broadly lanceolate, bounded by a strong keel to 

 the posterior end. Surface covered by numerous regular, well- 

 defined concentric furrows, and crossed by a few faint rays. 



Dimensions. Length 12 lines, width 16 lines, depth 8 lines. 



