LAMELLIBRANCHIATA. 409 



CONOCARDIUM, Bronn. 1835. 



CONOCARDIUM CUNEUS. 



PLATE LXVll, KIGS 1 3J ; I'LATE LXVIII, FIGS. 1, 4-16; AND PLATE XCIV, FIGS. U, 12. 



PleimirhyHchm nmeiis, CoyHAj). Geol. Surv. N. Y., Ann. Rep., p. 206. 1840. 

 Comx-ardium cuiteux (Cosvlw), S. A. Mii.lkr. Cat. Am. Pal. Foss., p. 187. 1S77. 



" " " H.\LL. Pal. N. Y., vol. V, pt. 1. Plates and Explanations ; PI. 67, figs. 21- 



27, 29-32. 1883. 

 Pletiri>rJiynchiiJi atUiiiuiius, CosRAD. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 253. 1.S42. 

 Conocardinm attenuatum (Conrad), S. A. Millkr. Cat. Am. Pal. Foss , p. 187. 1877. 



■' " Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 67, tigs. 



1-11. 1883. 

  Pleumrhynchus Mgonaliis, Hall. Geol. Surv. N. Y., Rep. Fourth Dist., p. 171, t. 67, tigs. 6, 6a. 1843. 

 Conocardinm trigmiale (Hall), S. A. Miller. Cat. Am. Pal. Foss., p. 187. 1877. 



" " " Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 67, fig. 28; pi. 68, 



tigs. (1?), 4-16. 1883. 

 ConiK-ardium, naxutum, Yi.Ki.h. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI 67, tigs. 12-20. 1883. 

 Bilobites, Dk Kay.* Ann. Ly. Nat. Hist. N. Y., vol. i, p. 45, pi. 5, figs. 1-4. 1824. 



Shell large, angularly sub-ovate, or trigonal in outline ; length less than twice 

 the height ; basal margin gently curving from the post-inferior extremity to 

 the anterior end. Posterior extremity abruptly truncate, produced into a 

 tubular extension along the cardinal line. Cardinal line straight, margins 

 inflected toward the anterior end. Anterior end more or less rapidly atten- 

 uate, with the margins gaping before reaching the extremity. 



Valves gibbous. 



Beaks sub-central, vertical, prominent and closely incurved over the hinge- 

 line. Umbonal slope angular, usually strongly defined, extending to the post- 

 inferior extremity. Post-cardinal slope flat or concave. 



Test thick, composed of two distinct layers. Surface marked by numer- 

 ous radiating plications and intermediate arching lamellose, concentric striga 

 on the bo<ly of the shell. The posterior slope is ornamented by curving 

 radii, extending from the beak to the posterior margin, with the interspaces 

 marked by transverse lamellose stria). From the entire periphery of the 

 umbonal ridge there extends a finely striated expansion of the shell, which 

 increa.ses in extent from the beaks downward, and in old shells is supported 

 anteriorly by a thickening of the shell along the basal margins, which often 



* Note on the Or^nic Remains termed Bjlobites, from the CatskiU Mountains. By J. E. Db Kay, M. D. 

 Read October 13, 1823. 



