316 PALAEONTOLOGY OF NEW YORK. 



In nearly all the well-preserved specimens of this species the beaks have 

 been eroded during life, as shown in figures on plate xciii. 



Formation and localities. In the shales of the Hamilton group, at Pratt's falls 

 and Delphi, Onondaga county ; in Schoharie, Otsego and Madison counties, 

 and on the shores of Seneca lake. 



NUCULA LIRATA. 



PLATE XI-V, FIGS. », 11, 15, 17-!H, 24, 28; AND PLATE XCUI, FIG. 6. 



Nucvlites lirata, Conrad. Jour. Acad. Nat. Sci. Phila., vol. viii, p. 250, pi. 15, fig. 7. 1842. 



Nueula luieatat (Phillips), Hall. Geol. Surv. N. Y., Rep Fourth Dist., p. 197, No. 78, fig. 5, p. 196. 



1843. 

 Nnevla lirata (Conbad), Hall. Prelim. Notice Lamellibranchiatn, 2, p. 3. 1870. 



" " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 45, figs. 17-27. 1883. 



Not Nueula lineata (Phillips). Paljeozoic Fossils, p. 39, pi. 18, fig. 64. 1841. 



Shell of medium size, ovate-triangular; length from one-third to one-fourth 

 greater than the height; basal margin regularly curving, more abruptly 

 rounded at the posterior extremity ; cardinal margin slightly arcuate, grad- 

 ually sloping toward the posterior. Anterior end short, sub-truncate, usually 

 abruptly rounded. 



Valves very gibbous, ventricose in the umbonal region. 



Beaks, at the anterior third or fourth of the length of the shell, distant, 

 elevated, rising considerably above the hinge-line. Umbo very prominent. 

 Umbonal slope elevated and rounded, merging into the general convexity 

 before reaching the posterior end. 



Test thick, marked by regular, strong, sub-angular concentric undulations, 

 which are crossed by extremely fine radiating striae. In older shells the 

 margins are marked by fine, concentric striae, the strong undulations having 

 become obsolete. 



The characters of the interior are strongly marked, as shown in figs. 24, 

 25, plate xlv. 



A specimen preserving both valves in contact has a length of 21 mm., 

 height 14.5 mm., and depth of both valves 12 mm. Three separate valves 

 measure respectively 22, 20 and 18 mm. in length, and 17, 15.5 and 12 mm. 

 in height. 



