INVERTEBRATE PALAEONTOLOGY. 489 



until we can have an opportunity to study and compare additional speci- 

 mens in a better condition, it may as well be viewed, at least as a variety oi 

 thai species. 



Localiti/ and position. — The original specimen of this species was found 

 at the Great Bend of the Missouri River below Fort Pierre; in the lower part 

 of the Fort Pierre group of the Upper Missouri Cretaceous series ; and 

 the specimen figured by us also came from the same locality and horizon. 



NAUTILIDiE. 



Genus NAUTILUS, Linnaeus. 



Synon.— Nautilus, Linnaeus (1758), S.vst. Nat. (ed. 10), 709.— Bruguiere (1789), Encyc. Mcth., I, xiv.— 

 Cuvier (1798), Tali, filem., 332.— Lamarck (1799), Prodr., 79; ami (1801) Syst., 99; 

 also (1805) Ann. Mus., V, 179 ; also (1809) Phil. Zool., and (1822) Hist., VII, 630.— limit f. 

 (1808), Conch. Syst., 1,2.— J. Sowerby (1812), Min. Conch., 1, 13.— Blainville (1822), 

 Diet. Sci. Nat . XXXII, 183 ; and ( 1825) Malac, 387.— Desbayes (1824), Coij. Fos?. Euv. 

 Paris, II, 707; and (1866) Suppl. to same, 111,622.— Owen (1832), Memoir on the 

 Pearly Nautilus, Loudou, 4.— Broun (1837), Leth., 104, 176, and 1122. — Agassiz and 

 Desor (1840), German tr.insl. Sowerby's Min. Conch.,27.— D'Orbigny (1840), Paleont. 

 Fr., 1,70.— Pictet (1854), Traite de Paleont. II (2e e"d.), 622.— Gabb (1864), Palasont. 

 Cal., I, 59.— Meek (1805), Palaiont. Upper Missouri, 64.— Blanford (1866), Palseont. 

 Indica, I, 6.— Stoliczka (1866), ib., 202.— Zittel (1868), Pateont. Mitth. aus dem Mus. 

 des Koenigl.-Bayer. Staates, 41 ; aud of many others. 



Angulites, Bisiphitcs, Oceanus, and Ammonites, Moutfort (1808), Conch. Syst., I, 6, 54,58, aud 74 

 (not Ammonites, Breynins, and others). 



Simplegas (sp.), Blainville (1824), Diet. Sci. Nat, XXXII, 185; and (1825) llajac.,385; also (1827) 

 Dict.,XLIX, 248 (uot Simplegades, Moutfort, 1808). 



Omphalia, De Hann, Monogr. Animon., &c., 51. 



Discites, De Hann (1825), ib. — McCoy (1844), Synop. Carb. Fossils Ireland, 54 (not Discites, 

 Schloth., 1820 ; nor Goldfuss, 1830). 



TcmnocMIus, McCoy (1844), Synop. Carb. Fossils Ireland, 20. — Meek and Worthen (I860), Illinois 

 Geo]. Survey Reports, II, 162 (adopted as a subgenus uuder Nautilus). 



Discus, Kiug (1844), Ann. aud Mag. N. H., XIV (old ser.), 274.— Meek and Worthen (1860), 

 Proceed. Acad. Nat. Sei. Philad.,XII, 469 (adopted as a subgenus under Nautilus); not 

 Discus, Fitzinger, 1833; nor Haldeman, 1840. 



Crijptoceras, d'Orbigny (1850), Conra Elemeut,, 1, 286.— White and St. John (1869), Trans. Chi- 

 cago Acad. Sci., I, 124 (as a subgenus uuder Nautilus) ; uot Cryptoccras, Latreille, 

 1804 ; nor Barrande, 1846. 



Trematodiscus, Meek and Worthen (1861), Proceed. Acad. Nat. Sci. Philad., XIII, 147 ; and Illi- 

 nois Geol. Survey Reports, II, 161 (proposed as a subgeuus under Nautilus). 



Endolobus, Meek and Worthen (1865), Proceed. Acad. Nat. Sci. Philad., XVII, 259 ; and Illinois 

 Geol. Survey Reports, II, 307 (proposed as a subgenus under Nautilus). 



Hercoglossa, Conrad (1806), Am. Jour. Conch., II, 101. 



Solenochilus, Meek and Worthen (1870), Proceed. Acad. Nat. Sci. Philad., XXII, 47; also (1873) 

 Illinois Geol. Survey Reports, V, 524, and 544 (proposed as a subgenus under 

 Nautilus). 



Ftt/m. — vaVTiKoc, a sailor. 



Type. — Nautilus pompilius, Linnaeus. 



Shell involute, globose, discoid or variously compressed ; umbilicus 

 closed, or more or less widely open, sometimes perforated in the middle; 

 volutions oval, rounded, compressed or angular, all coiled on the same plane, 

 C2 II 



