482 CRETACEOUS PALEONTOLOGY. 



1834. Pecten quinqitecostatus Mort., Synbp. Org. Rem. Cret, 



Gr. U. S., p. 57, pi. 19, fig. i. 

 1838. Pecten quinqucco status Bronn, Lethaea Geog., Zweiter 



Band, pp. 678-680, taf. 30, fig. 17. 



1849. Pectetit qvadricosfatus Roem., Texas, p. 398. 



1850. Janira mortonii d'Orb., Prod. Paleon. Strat., vol. 2, p. 



253- 



1852. Pecten quadricostatus Roem., Kreide von Texas, p. 64. 

 1852. Pecten quadricostatus var. Roem., Kreide von Texas, p. 



64, pi. 8, figs. 4a-c. 

 1854. Pecten quadrico status Shum., Marcy's Expl. Red River 



La., p. 178, pi. 2, figs. 2a-b, pi. 3, fig. 6. 

 1861. Neithea mortonii Gabb, Proc. Acad. Nat. Sci. Phil. 



(1861), P- 365- 

 1861. Neithea mortonii Gabb, Synop. Moll. Cret. Form., p. 



i 88 (132). 

 1864. Neithea mortoni Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 7. 



1868. Neithea mortoni Con., Cook's Geol. N. J., p. 725. 

 1870. Pecten quadricostatws Credner, Zeitsch. Deutsch. Geol.. 



Ges., Bd. 22, p. 232. 

 1886. Neithea quinqu^costata Whitf., Pal. N. J., vol. i 



(Monog. -U. S. G. S., vol. 9), p. 56, pi. 8, figs. 12-14, 



Description. "Shell broadly ovate exclusive of the auricula- 

 tions, and plano-convex to concavo-convex in profile, right valve 

 strongly convex, with a sharp, arching, and incurved beak ex- 

 tending beyond and partially overarching the hinge-line; hinge- 

 line straight or nearly so, slightly declining on the anterior side;, 

 nearly two-thirds as long as the entire width of the shell ; auricu- 

 lations moderate in size, .the anterior one the smallest and con- 

 stricted below where it joins the body of the shell, forming a 

 slight byssal notch; posterior side triangular, longest at the 

 hinge-line and receding below. Sides of the valve, where it joins 

 the auriculations strongly incurved laterally, so as to cause the 

 sides to overhang. Valve marked by six strong, rounded, prin- 

 cipal radiating costse, with from two to four smaller ones be- 



