MOLLUSCA. 68s 



The umbilical shoulder is rounded, but just below the umbilical 

 margin, upon the slope into the umbilicus, the surface is abruptly 

 impressed, the outer thickened rim so formed being transversely 

 wrinkled or crenate. The single example described by Gabb as G. 

 abbotti is certainly not of specific value, and that species must be 

 considered as a synonym oif G. aby'ssina. The specimen from the 

 Vincentown formation at Timber Creek, which has been identified 

 as Natica abyssina by Whitfield, is doubtless a distinct species, 

 although the single specimen, an imperfect internal cast, is not 

 sufficient to show its specific characters fully. 



Formation and locality. — Navesink marl, Atlantic Highlands 

 (io8), near Crawfords Corner (126'), Crosswicks Creek (147*), 

 MullicaHill (1692). 



Geographic distribution. — New Jersey, Alabama, Texas. 



Gyrodes crenata Conrad. 



Plate LXXVII., Figs. 10-12. 



i860. Natica (Gyrodes) crenata Con., Jour. Acad. Nat. Sci. 



Phil, 2d ser., vol. 4, p. 289. 

 1861. Gyrodes crenata Gabb, Synop. Moll. Gret. Form., p. 116 



(60). 

 1861. Natica infracarinata Gabb, Proc. Acad. Nat. Sci. Phil. 



(i86i),p. 319- 

 1 861. Gyrodes Spill'mani Gabb, Proc. Acad. Nat. Sci. Phil. 



(1861), p. 320. 

 1864. Gyrodes crenata Meek, Check List Inv. Foss. N. A., Cret. 



and Jur., p. 21. 

 1864. Gyrodes SpiUmani Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 21. 

 1868. Gyrodes infracarinata Con., Cook's Geol. N. J., p. 729. 

 1892. Gyrodes infracarinta Whitf., Pal. N. J., vol. 2 (Monog. 



U. S. G. S., vol. 18), p. 125, pi. 15, figs. 13-16. 

 1892. Gyrodes crenata Whitf., Pal. N. J., vol. 2 (Monog. U. 



S. G. S., vol. 18), p. 126, pi. 16, figs. 5-6. 

 1905. Gyrodes crenata Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 21. 



