LAMELLIBRANCHIATA. 427 



with the Cardiola retrostriata (von Buch) of various authors, and with Cardium 

 palmatum of Goldfuss. Its citation by numerous authors shows its wide distri- 

 bution in Europe. 



Formations and localities. In the shales of the Hamilton group near Geneva, 

 Ontario county; Sherburne creek, Chenango county, and on the shores of 

 Cayuga lake. In the Genesee slate at Bristol, Ontario county, and numerous 

 other localities. In the Portage group at Branchport, Yates county ; and at 

 Ithaca, Tompkins county, N. Y. 



PRiECARDIUM, Barrande. 1881. 

 Pr^cardium vetustum. 



PLATE LXX, FIGS. 18-20. 



Ccardiwmf vetuxtmii. Hall. Geol. Surv. N. Y., Rep. Fourth Dist., p. 245, t. 107, fig. 2. 1843. 

 Cardiola vetiuta (Hall), 8. A. Millbr. Cat. Am. Pal. Foss., p. 186. 1877. 



PrcBcardium retiuitum, H&LU Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 70, figs. 18-20. 1883. 

 Compare " dexpectum, Barrandb. Syst. Silur. de Boh4me, vol. vi, pi. 285, III, figs. 5-8. 1881. 



Shell small, trigonal, arcuate, oblique ; length greater than the height. Ante- 

 rior margin concave, becoming rounded below ; basal margin gently curved. 

 Posterior margin contracted below, and obliquely truncate above. 



Valves moderately convex below, becoming gibbous in the umbonal region. 



Hinge-line declining posteriorly. 



Beaks anterior, prominent and strongly incurved. 



Surface marked by fine concentric striae and by from ten to fourteen strong 

 elevated flattened radii, which show a tendency to duplication on the ante- 

 rior end. Interspaces flat, as wide or wider than the radii. 



Three specimens measure respectively 17, 17 and 16.5 mm. in length, and 

 14, 10.5 and 13 mm. in height. 



This is a smaller species, but very similar to Pmcardium despectum, of Bar- 

 rande, loc. cit. 



Formation and hcality. In the shales of the Portage group on the shore of 

 lake Erie, near Portland Harbor, N. Y. 



