340 DR WHEELTON HIND ON THE LAMELLIBRANCH AND 



Dimensions. — PI. I. fig. 14. Specimen No. 15,731, a left valve, measures: antero- 

 posteriorly, 18 mm. ; dorsoventrally, 17 mm. 



Locality. — Millstone Grit of Hazel Hill, 5 miles N.E. of Pately Bridge, Yorkshire ; 

 and possibly Congleton Edge Quarry, Cheshire. 



A single specimen, a left valve, is in the collection of the Geological Survey, Jermyn 

 Street, from the Millstone Grit of Hazel Hill, Yorkshire. 



Observations. — The specimen which I now refer to this species is fairly well preserved, 

 but has the tips of each ear wanting. At the lower margin the ribs are seen to project 

 as spines, but the matrix is too hard and coarse to make out whether the spines curved 

 upwards as they are shown to do in Meek and Hayden's figure. The only other British 

 Carboniferous example which is known to have had projecting ribs is A. Murchisoni 

 (Brit. Carb. Lamell., vol. ii. pi. xiv. fig. 4), a species which more closely resembles the 

 American shell than any other of the genus. Mkek and Hayden describe the right 

 valve as nearly flat, with surface markings as in the left valve but more obscure. 



Two fragments in my possession from the Congleton Edge Quarry, upper part of 

 the Pendleside series, probably belong to the species, although not present in the Scotch 

 collection. I have inserted the description of A. carboniferus here because it is a 

 member of the American fauna. 



Aviculopecten obliquus, sp. nov. (PI. I. fig. 8.) 



Specific Characters. — Shell small, oblique ; body of the valve ovate, acute. The 

 right valve convex. The anterior margin is short and convex. The inferior descends 

 and is broadly convex. The postero-inferior part of the valve produced and bluntly 

 rounded. The line which forms the margin from the umbo to the postero-inferior angle 

 is almost straight, and defines the valve from the posterior ear. The hinge line is 

 straight, long, produced posteriorly into an acute point. The umbones are small, 

 pointed, level with the hinge line, and placed very slightly anterior to the centre of the 

 hinge line. The anterior ear is depressed, rolled, comparatively large and deep, separated 

 from the valve by a fold and notch. The posterior ear is much compressed, triangular, 

 pointed, its margin falcate. 

 Interior. — Not exposed. 



Exterior. — The right valve is ornamented by many thick, nodulose, radiating ribs, 

 between each pair of which linear plain ribs are intercalated. The anterior ear has a 

 few radiating ribs ; the posterior, fine concentric lines of growth. 



Dimensions. — PL I. fig. 8. Specimen No. T4507 B , a right valve, measures : antero- 

 posterior^, 12 mm. ; dorso-ventrally, 12 mm. 



Locality. — Midlothian, Bilston Burn near Polton, bed 27 to 30 feet above Castlecary 

 Limestone. 



Observations. — Unfortunately only right valves of this species have been found. 

 The nodular ornament is very well marked. One specimen, which consists of the fossil 

 and its counterpart, shows an almost perfect shell ; the other is a cast of the exterior. 



