INVERTEBRATE PALEONTOLOGY. 413 



larger end, and 0.07 at the smaller; while the smaller limb measures near 

 the curve 0.05 inch in diameter. 



I have described this little shell as if only folded once upon itself, so as 

 to form only two limbs; but this is done simply because only one folding is 

 to be seen in any of the imperfect specimens examined. As they are all 

 broken, however, at both ends, it may possibly have folded back upon itself 

 again in adult specimens. In such cases, of course we can only describe 

 what we see. It is remarkable for the simplicity of its septa-lobes and 

 sinuses, and the small size of its antisiphonal or inner lobe; the other known 

 species having these parts more branching and digitate, and the inner lobe 

 proportionally larger. I know of no other described species nearly enough 

 related to it to render a critical comparison necessary. 



Locality and position. — Great Bend of the Missouri Eiver below Fort 



Pierre; from the lower part of the Fort Pierre group of the Upper Missouri 



Cretaceous series. 



SCAPHITID^E. 



Genus SCAPHITES, Parkinson. 



Synon.— Scaphites Parkinson (1811), Org. Rein., Ill, 145.— J. Sowerby (1812), Min. Conch., 1, 53— Fe"russ. 

 (1821), Tab. Syst., XIX.— Blainv. (1824), Diet. Sci. Nat., XXX, 190 ; and Malae., 384 

 and 623.— D'Orbigny ( 1826), Tab. des Cc'phal. ; and (1841), PaMont. Francaise, I, Terr. 

 Cret., 512.— Defr. (1827), Diet. Sci., Nat., XLVIII, 28.-Menke(1828), Synon. ; and (1830) 

 ib. (2e ed.).— Desbayes (1832), Kncyc. M<>tb., Ill, 933.— Bronn (1839), Letb., 727.— 

 Gray (1842), Synon. Brit. Mus.,92. — Geiuitz (1845),Grundr. d. Verst.,301 (as a sub- 

 genus under Handles. ).— Qnenstedt (1852), Haudb. der Petref., 377. — Chenu (1859), 

 Man. de Conch., 1, 91.— Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 

 281 ; and (18G0) ib., XII, 420.— Binkhorst (1861), Monogr. des Gasteropodes et des 

 Cepbalopodes de Craie Sup. du Limbourg, 38.— Favre (1869), Moll. Foss. de la Craie 

 des Environs de Lenjburg, 18. 



Scaphita, Flem. (1828), Hist. Brit. Ann., 249. 



Discoscaphites, Meek (1872), in Hayden's Sec. Ann. Rep. U. S. Geol. Surv. of the Territories, 297 (as 

 a subgenus under Scaphites). 



Etym. — OK.a<p!i, a small boat. 

 Type. — Scapkites oequalis, Sowerby. 



Shell oval, subcircular or elliptic in general outline, more or less com- 

 pressed or sometimes gibbous ; volutions contiguous or variously embracing 

 in young shells, but last one in the adult more or less deflected and extended 

 from the others, and finally curving backward again ; aperture oval or sub- 

 circular; lip with a small rim or inflection, but without appendages; septa 

 symmetrical, regularly divided into from four to six lobes and sinuses, nearly 

 always with paired branches, excepting the inner lobe, which is often very 



