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Show 373 tinguish these forms. When we compare the septa, however, they are at gnce seen to present marked differences, such as are clearly incompatible with specific identity, if d'Orbigny's figures are accurately drawn. It is also closely allied to A. Moretianus, d'Orbigny, but differs in the structure of its septa. A Locality and position.- Cretaceous beds at Komooks, Vancouver's Island; also in the lower division of the California Cretaceous at Cotton-wcxkl Creek, Shasta County, of that State. Genus NAUTILUS, Linnams. NAUTILUS OAMPBEIXI, Meek. Pl* te6, figB. 2* zid2 « . . Na* tilus CampbcW, Meek ( 1801), Proceed. Aoad. Nat. Sci. Pbilad., 318. Shell large, subglobose, or somewhat oval, moderately convex; periphery and sides rounded or slightly oompressed; volutions increasing rather gradually in size, deeply embracing, and rounding into the umbilicus on each side; umbilicus very small, but not quite closed; septa separated by spaces less than one- third the transverse diameter of the whorls at the point of measurement, arching slightly backward on the sides and periphery; aperture nearly circular, but deeply sinuous on the ventral side for the receptions of the inner whorls. Siphuncle and surface- markings unknown. Length, or greatest diameter, 4.83 inches; breadth, or transverse diameter, 3.07 inches. • This fine Nautilus is much like N. dementinus, d'Orbigny, as figured in his Pal6ont. Frangais, Terr. Cr6t., i, pi. 13 bis. It differs, however, in having a more rounded aperture and a more broadly- rounded periphery, the entire shell being less compressed. It is perhaps more nearly allied to some varieties of the Indian form referred by Dr. Stoliczka to N. Bouchardianus, d'Orbigny (=* N. Icsvigatus and N. spharicuSj Forbes), some of which seem to be nearly as much compressed. None of these forms, however, show near so rounded an aperture or section of the volutions. Yet it is extremely difficult to distinguish these smooth Nautili of this type with such specimens as we usually get for study, and it is therefore possible that more extensive collections may show it to be necessary to unite the Vancouver shell with one of these foreign species. It may be at once distinguished from Nautilus Dekayi ( which has been ^ identified by Dr. Shumard from Vancouver's Island) by its much more compressed form, narrowed aperture, and slightly open umbilicus, that of N. Dekayi being entirely closed at all ages by a solid shelly columella. Its whorls are also more compressed on the sides, and more concave in the region of the umbilicus, thus giving a very different form to its aperture and the section of its volutions. The specific name was given in honor of Mr. Archibald Campbell, the commissioner in charge of the Northwestern Boundary Survey. I have given on the same plate ( Fig. 3) for comparison, an outline showing a transverse section of one of the whorls of Nautilus Dekayi, taken from Dr. Morton's original specimen, in the collection of the Academy of Natural Sciences at Philadelphia. Locality and position.- Komooks, Vancouver's Island; Cretaceous. |