PTEhMXOPECTEX DUMONTIAXl'S. 65 



long time I was doubtful as to the value of this species, and could find no other 

 specimens. However, in Mr. Wright's cabinet I observed a series of four small 

 shells which are certainly like Phillips's shell, and have a peculiar and characteristic 

 ornament. 'The type seems to have losl must of its shell, and to be in the form of 

 a cast of the interior, but the test over the posterior ear remains. The ornament 

 is of a very open basket-work character. One of Mr. Wright's specimens shows 

 both valves, and the right valve proves to be flat, with much the same ornament as 

 the left valve. 



The generic affinity of this species is not very certain, but the absence of 

 posterior ear and the length of its hinge-line have induced me to place it for the 

 present under Pterinopecten. 



Ptickinopecten Dumontiantjs, de Koninck, sp., 1843. Plate VIII, figs. 4 — 8; 



Plate XIV, figs. 1 , 2. 



Pecten Dumontiana, de Koninclc, 1843. Descr. Anim. Foss. Terr. Carb. Belg., 



p. 134, pi. iv, fig. 3. 

 Avictjla Valenciennesiana, de Koninclc, 1851. Ibid., Suppl., p. 681, pi. lvii, 



fig. 2. 

 Aviculopecten Dumontiantjs, Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 164. 

 de Koninclc, 1885. Ann. Mus. Roy. d'Hist. Nat. 



Belg., torn, xi, p. 212, pi. xxxvii, fig. 3. 



Specific Characters. — Shell above medium size, the left valve subrotundato- 

 trapezoidal, moderately convex, the right valve much less so. Antero-posterior 

 diameter less than dorso-ventral diameter, but variable. Anterior margin more 

 rounded than the posterior margin, which is sinuous above and falciform imme- 

 diately below the upper margin. The hinge-line straight, elongate, produced back- 

 wards, and pointed. The umbones gibbose, small, pointed and incurved, much less 

 marked in the right valve, and placed at the junction of the anterior and middle 

 thirds of the hinge-line. The anterior ear depressed, well marked off from the 

 valve, triangular, its margin rounded, of fair size; the posterior ear not marked olT 

 from the valve, but continuous with the compressed and expanded postero- 

 superior angle of the valve, with which it is incorporated. 



Interior. — Unknown. 



Iirlcri<n\ — The surface of the left valve is ornamented with many thick, nodular, 

 radiating ribs, which alternate with somewhat thinner ones, crossed by occasional 

 concentric undulations of growth. The anterior ear is marked transversely by 

 aboul six radiating ribs, crossed by numerous concentric lines of growth. In the 

 right valve tin' alternately large and small radiating ribs are more numerous, closer, 



