INVERTEBRATE PALAEONTOLOGY. 44."> 



consisted only of the inner turns. The perforated character of the umbilicus, 

 mentioned by Dr. Morton, is merely due to Ihe accidental breaking-through 

 of the small, slender, inner volutions of his specimens. 



Locality and position. — Dr. Morton's type-specimens of this form were 

 from t lie Missouri River, Dakota ; exact locality not mentioned. Ours were 

 found on Moreau River, Dakota, where they occur in the Fox Hills group of 

 the Upper Missouri Cretaceous series. 



Scaphites 1*1 a n «1 a n r n s i <s , Morton (sp.). 



Plate 35, figs. I, «, b, c. 



Ammonites Mandanensis, Morton (1841), Jour. Acad. Nat. Sei. Pbilad., VIII, 208, pi. 10, tig. 2. 

 Ammonites ? Mandanensis, Owen (1852), Report Wisconsin, Iowa, and Minnesota, tab. 7, rig. 5. 

 Scaphites Mandanensis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Pbilad., VIII, 281. 



Shell short-oval, or subcircular, much compressed; volutions six to six 

 and a half, increasing rather gradually in size from within ; last one not 

 much enlarged, and scarcely deviating from the curve of the others, flattened 

 on the sides and periphery, and angular and ornamented by a row of very 

 small crenatures around the umbilicus, and another of little nodes on each 

 side of the periphery, excepting near the aperture; each inner whorl partly 

 received within the rather deep dorsal groove of the succeeding turn ; um- 

 bilicus rather wide, and exhibiting a part of each inner whorl ; aperture oval- 

 subcordate, being longer than wide ; surface ornamented by small, slightly 

 flexuous costse, which increase by intercalation and division so as to number 

 about three times as many at the periphery as around the umbilicus; costse 

 becoming much finer and more closely arranged near the aperture. 



Length, 1.84 inches; height, 1.43 inches; 'convexity, 0.59 inch. 



Usually, each one of the costas of this shell terminates at one of the little 

 nodes along the angular margins of the narrowly-flattened periphery ; but 

 where the nodes become larger and more distant, along this part of the last 

 or body volution, sometimes two of the costse coalesce at one of these mar- 

 ginal nodes, while others pass between them. In crossing the narrow periph- 

 ery of the last whorl, all the costye arch a little forward. 



The sutures of the septa in this species are so very similar to those of 

 that last-described form, that it would be almost an exact repetition of the 

 same words used in the description of that form, to describe them in detail. 

 Yet slight differences in the details of the lobes and sinuses might be men- 



