64 CARBONIFEROUS LAMELLIBRANCHIATA. 



Observations. — The type specimen of P. tessellatus, Phillips, sp., is preserved in 

 the Gilbertson Collection, Natural History Museum, South Kensington, and I am 

 permitted to re-figure it in PI. IX, fig. 10. It is a left valve, not quite complete 

 posteriorly, bat the restored contour was correctly indicated in Phillips's figure 

 already quoted. I have been fortunate enough to meet with a right valve in the 

 Burrows Collection of the "Woodwardian Museum, Cambridge, which, however, has 

 lost its anterior ear. I have also figured (PI. IX, fig. 9) a perfect but young 

 example from the collection of Mr. J. Wright. It is rather smoother, but has a 

 similar ornament to that possessed by the left valve. 



Incomplete specimens of P. tessellatus may be easily confounded with A. nobilis, 

 de Koninck, which has much the same ornament ; but the latter shell has the 

 shorter hinge-line of Aviculopecten, and belongs to that genus. Its shape is more 

 generally ovate, and has a definite but shorter posterior ear than the present 

 species. 



Pterinopecten cyclopterus, Phillips, sp., 1836. Plate XVII, figs. 15 — 19. 



Avicula cycloptera, Phillips, 1836. Geol. Yorks., pt. ii, p. 211, pi. vi, fig. 5. 



Specific Characters. — Shell small, the left valve gibbose, the right flattened, 

 with flattened and produced ears, U-shaped. The hinge-line straight and produced 

 at each end, the longest diameter of the shell. Umbo swollen, incurved, and 

 pointed, twisted slightly forwards, placed a little in front of the centre. Ears 

 not Avell defined, gradually compressed and expanded, the posterior larger than 

 the anterior ear. 



Interior. — Unknown. 



'Exterior. — The surface is ornamented with few distant, radiating ribs, hardly 

 elevated above the rest of the valve, secondary ribs arising in large examples 

 towards the lower margin of the valve. These ribs are crossed by strong, concen- 

 tric, rounded, distant folds, which are continued up to the hinge-line, and strongly 

 marked on each ear. 



Dimensions. — PI. XVII, fig. 15, the type, a left valve, measures — 



Antero-posteriorly . . . .23 mm. 



Dorso-ventrally . • • .23 mm. 



Localities. — England: the Carboniferous Limestone of Yorkshire (Bolland). 

 Ireland: (he Carboniferous Limestone of Little Island, co. Cork; Dromore, co. 

 Limerick. 



Observations.^ The type specimen is a left valve (PL XVII, fig. 15) preserved in 

 the Gilbertson Collection, Natural History Museum, South Kensington. For a 



