372 Systematic Paleontology 



EUTREPHOCERAS DEKAYI (Morton) 



Plate XIII, Fig. 9 



Nautilus dekayi Morton, 1833, Am. Jour. Sci., 1st ser., vol. xxiii, p. 291, pi. 



viii, fig. 4. 

 Nautilus dekayi Morton, 1834, Syn. Org. Rem. Cret. Group U. S., p. 33, pi. 



viii, fig. 4; pi. xlii, fig. 4. 

 f Nautilus perlatus Morton, 1834, Syn. Org. Rem. Cret. Group, U. S., p. 33. 

 Nautilus dekayi Hall and Meek, 1856, Mem. Am. Acad. Arts and Sci., Bos- 

 ton (n. s.), vol. v, p. 406. 

 Nautilus dekayi Meek and Hayden, 1856, Proc. Acad. Nat. Sci., Phila., vol. 



viii, p. 280. 

 Nautilus dekayi Meek, 1859, Northwest Terr., Rep. Prog. Assinaboia and 



Saskatchewan Expl. Exped., H. Y. Hind., p. 91, pi. ii, figs. 9, 10. 

 Nautilus dekayi Conrad, 1860, Jour. Acad. Nat. Sci., Phila., vol. iv, p. 276. 



(Not N. dekayi as figured by Ernest Favre in Moll. Foss. Craie Env. 



de Lemberg, pi. iii, figs. 1-3.) 

 Nautilus dekayi Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur., 



p. 25. 

 Nautilus dekayi Conrad, 1868, Cook's Geol. of New Jersey, p. 731. 

 Nautilus dekayi Gabb, 1876, Proc. Acad. Nat. Sci., Phila., 1876, p. 277. 

 Nautilus dekayi Meek, 1876, Rept. Inv. Cret. and Ter. Fossils, Up. Missouri, 



p. 496, pi. xxvii, figs, la-lc. 

 Nautilus dekayi "Whitfield, 1892, Mon. U. S. Geol. Survey, vol. xviii, p. 243, 



pi. xxxvii, figs. 1-6; pi. xxxviii, figs. 1-4. 

 Eutrephoceras dekayi Hyatt, 1894, Proc. Am. Phil. Soc, vol. xxxii, p. 555, 



pi. xiii, figs. 4-8; pi. xiv, fig. 1. 

 Eutrephoceras dekayi Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 28. 

 Nautilus dekayi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 



817, pi. c, figs. 1-5. 



Description. — " Shell very ventricose, with numerous undulated, trans- 

 verse stria>; aperture laterally and profoundly expanded." — Morton, 1834. 



" Shell subglobose, broadly rounded on the periphery and sides ; umbili- 

 cus closed ; volutions increasing rapidly in size, or more than doubling 

 their diameter each turn, about half as wide again as high, all hidden but 

 the last or outer one ; aperture much wider than long, transversely reni- 

 form, the lateral extremities being rounded, and the inner side deeply 

 sinuous for the reception of the inner whorls ; lip having a wide sballow 

 sinus along the peripheral side, prominently rounded on the lateral mar- 

 gins, and again sinuous near each umbilicus ; septa moderately concave, 

 and about sixteen or eighteen to each turn ; siphuncle small, located one- 

 fourth to one-third of the distance across toward the periphery, from the 



