10G CARBONIFEROUS LAMELLIBRANCHIATA. 



Pseudamusiom gibbostjm, M'Goij, sp., 1844. Plate XXI, fig. 12. 



Pecten gibbostjs, M'Coy, 1844. Synops. Carb. Foss. Ireland, p. 93, pi. xviii, 



fig. 5. 



Specific Characters. — Shell small, orbicular, very convex, the contour from ear 

 to ear nearly circular. The hinge-line straight, fairly long. The umbo tumid, 

 incurved, and pointed, raised above the hinge-line in the left valve. The ears 

 narrow and elongate ; the anterior ear deeply separated from the valve by a curved 

 groove, the posterior ear with its posterior superior angle a right angle. 



Interior. — Unknown. 



Exterior. — The surface of the left valve is ornamented with fine, microscopic, 

 radiating Hues apparent only on the anterior third of the valve ; there are also 

 very fine, close, concentric lines visible with the microscope. The ears appear 

 to be smooth. The right valve has a similar ornament. 



Dimensions. — PI. XXI, fig. 12, a left valve from Castletou, measures — 

 Antero-posteriorly . . . .20 mm. 



Dorso-ventrally . . . .20 mm. 



Gibbosity of the valve . . .5 mm. 



Localities. — England : the Carboniferous Limestone of Castleton, Derbyshire. 

 Ireland : Bally duff, Dungarvan, co. Waterford. 



Observation*. — I am doubtful if the type of M'Coy's Pecten gihbosus is preserved 

 in the Griffith Collection, Science and Art Museum, Dublin. The specimen is a 

 left valve, much larger and much flatter than the figure, which represents a right 

 valve, and the ears are much longer than those in the figure. I have only met with 

 one other specimen of this species, a left valve. M'Coy's description is very 

 definite and accurate; his observations on the species are: — •" This little species 

 is almost globular. The small lengthened ear is perfectly flat, and distinctly 

 separated from the body of the shell." 



PsEUDAMTTsiUM fitbeillosum, Salter, sp., 1864. Plate XVI, figs. 1G — 22. 



Aviculopecten eibrillosus, Salter, 1864. Mem. Geo]. Survey, Geol. of Country 



round Oldham, p. 65, pi. i, fig. 2. 



Pecten prtetenuis, von Koenen, 1879. Neues Jahrb. f. Min., p. 329, taf. vi, 



figs. 3, 4. 



Aviculopecten Cairnsii, Bolton, 1897. Mem. Manch. Lit. and Phil. Soc, vol. xli, 



No. 6, p. 3. 



Pecten (pleuronectites) cf. pr^tenuis, Wolterstorff, 1899. Untercarbon. Mag- 



deburg-Neustadt, p. 47, pi. iii, 

 figs. 8—16. 



