BIVALVIA. 125 



HINNITES ABJECTUS, Phil, sp. Tab. IX, fig. 7, and Tab. XIV, fig. 3. 



PECTEN ABJECTUS, Phil. Geol. York., 1, t. 9, f. 37. 



Morris, Cat. Brit. FOBS., 1854, p. 175. 



Testa suborbiculari convexd ; auricula anticd productd lineatd, posticd subobsoletd; cos- 

 tellis rddiantibus numerosis (SO ad 100) irregularibus incequalibus nodulosis et transverse 

 striatis ; interstitialibus interdum lineisque tenuissime notatis ; valvd prope mediant costellis 

 2 vel 3 elevatis acutis sed nodulosis instructd. Valvd alterd planatd, delicatissimd lineis 

 tenuissimis et undulatis non nunquam obsoletis. 



Shell, when not distorted, sub-orbicular and convex ; the umbones small and depressed ; 

 the anterior auricle produced, the other usually indistinguishable ; the radiating little 

 costae are very numerous, (from 80 to 100,) irregular, unequal, nodulous, and transversely 

 striated ; the interstitial spaces have likewise more minute costse or lines, which are also 

 nodulous, unequal in size, and uncertain in number ; the auricle has these fine irregular 

 lines ; there will also constantly be noticed, towards the middle of the valve, two or three 

 costse, which are larger and more elevated than the others, they are acute but nodulous, 

 and will alone at once serve to distinguish the species from Hinnites velatus, to which the 

 general character of the surface offers a considerable resemblance. The figure of the 

 latter and smaller species, however, is more fan-shaped or less orbicular and less convex. 

 The other valve, which is very rarely seen, is extremely delicate and flattened, its surface 

 has numerous very fine waved radiating lines, which are occasionally indistinct. 



The numerous examples which we have obtained of this imperfectly known species 

 exemplify its extreme irregularity of contour and convexity, not one is altogether regular ; 

 the test is thin, and there can be no doubt that it readily assumed the figure of any surface 

 to which the flat valve was attached. In young examples the two or three more elevated 

 costae form a conspicuous feature which becomes less remarkable with the increase of the 

 dimensions. Our largest example is upwards of four inches across. 



Geological position and localities. Hinnites abjectus is found in the Coralline Oolite of 

 Malton, in the Great Oolite of Whitwell, and in the Inferior Oolite of Glaizedale, 

 Yorkshire ; it is also not uncommon in the upper division of the Inferior Oolite of 

 Gloucestershire, but it has only occurred very rarely in the Great Oolite of the Minchin- 

 hampton district. 



PHOLAS. Linn. 1758. 



Shell elongated, sub-cylindrical, gaping at both the extremities; umbones incurved and 

 contiguous. Hinge thickened, reflected to form a plate which covers the umbo in each 

 valve ; internally it has a curved spatulous tooth which projects in each valve. 



