418 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



II. Gland double, with the Aptychus calcareous. 



i. Aptychus furrowed externally : Ha/poceras, Waag. ; CEkotraustes, 



Waag. ; Oppelia, Waag. ; Haploceras, Zitt. ; ! Scaphites, Park. 



ii. Aptychus thin, granulated externally : Stephanoceras, Waag. ; 



Perisphinctes, Waag. ; Peltoceras, Waag. ; Cosmoceras, Waag. 

 Hi. Aptychus thick, smooth, and punctate externally : Si?noceras, 

 Zitt. ; Aspidoceras, Zitt.* 

 Not having had an opportunity to examine the evidence on which these 

 conclusions are based, I am unprepared to express any opinion of my own in 

 regard to them. I presume, however, that the grouping proposed by Pro- 

 fessor Waagen is only intended to be provisional, as it can hardly be sup- 

 posed, even if the nature and functions of these fossils could be regarded as 

 definitely settled, that their presence and peculiarities in a sufficiently large 

 number of species of certain groups, or their entire absence from a sufficient 

 number of those of others, have been determined, to warrant the conclusion 

 that future discoveries may not bring to light facts requiring modifications in 

 this proposed grouping of the genera. 



I observe that Professor Waagen places Scaphites with a mark of doubt 

 in the section of genera having a calcareous Aptychus. If Scaphites Chey- 

 ennensis, described farther on, really belongs to this genus, however, it would 

 probably be an exception to the rule, as we have every reason to believe 

 that its Aptychus was corneous. It belongs, however, to a peculiar group, 

 that possibly ought not to be admitted into the genus Scaj)hites. 



Scaphites larvseformis, M. & H. 



Plate 6, tigs. 6, a, b, c. 



Scaphites larvcformis, Meek aud Hayden (185fi), Proceed. Acad. Nat. Sci. Pliilad., VIII, 58; and (1860) «6., 

 XII, 420.— Meek (1864), Smithsonian Cleck-List N. Am. Cret. Fossils, 24. 



Shell small, transversely subovate, compressed, evenly rounded on the 

 periphery; volutions slender, nearly round, the inner or coiled ones forming 

 only a very small part of the entire shell, and so closely involuted as to leave 

 only a very small umbilical pit ; extended body-portion rather long, slender, 

 and straight to the recurvature, thence continued backward until it comes 

 nearly in contact with coiled inner volutions; aperture apparently circular; 



* Professor Baird's Ann. Record Sci. and Industry for 1873 (issued in 1874), p. 334. 



