398 DESCRIPTIONS OF NEW SPECIES OF FOSSILS, 



This fossil resembles tlie fragment figured by Dr. Morton as Ammonoceratites Con- 

 radii, {Jour. Acad. Nat. Sci., Vol. Till. p. 212, PI. X. fig. 1,) but diflers from that in 

 curving more abruptly, and could scarcely have formed a circle if continued. It differs 

 also in the bifurcation of the costae. 



It is with some hesitation that we refer this fragment to the genus Ancyloceras, but 

 the form of the curvature and character of the annulations more nearly resemble the 

 species of this genus than any other Avhich we know. 



Locality and Position. — Great Bend of the Missouri. Division No. 4 of Section. 



Baculites ovatcs and B. compressus of Say. 



These two species of Baculites were first described by Say, and subsequently recog- 

 nized and redescribed by Dr. Morton, who quotes Say's descriptions, in his Synopsis of 

 the Cretaceous Fossils of New Jersey. The Baculites ovatus had also been recognized 

 by the last-named author as occurring in the cretaceous formation in Alabama, as well 

 as in New Jersey and Delaware, showing a wide geographical distribution. The 

 B. compressus, regarded by Dr. Morton as a closely allied or perhaps identical species, 

 has been recognized only, so far as we know, in the cretaceous formation of the Upper 

 Missouri, from whence it was first described by Mr. Say. 



Dr. D. D. Owen, in his report on Wisconsin, Iowa, and Minnesota, has figured (PL 

 VII. fig. 6) a specimen which he refers with doubt to B. comjyressus of Say. The 

 specimen in question is from Sage Creek, Nebraska, and is a fragment apparently of 

 the outer chamber with the shell preserved ; and as no septa are shown, it is impossible 

 to determine satisfactorily its relations. On the same plate, fig. 7, another fragment is 

 given, also without septa, and, owing to the bad state of preservation, it shows no char- 

 acters by which it can be identified with any known species. 



The descriptions and figures above cited comprise the amount of our present 

 knowledge of these two species of Baculites. 



In our collections from Sage Creek, and from various localities along the Missouri 

 River, we have a considerable number of well-preserved specimens of Baculites, which 

 by their external characters are readily referred to two distinct species, one presenting 

 in its section a regular ovate form, or sometimes a little flattened on the more obtuse 

 or ventral side, the other presenting a section of very depressed ovate form. These 

 two forms are found to be characterized by internal difiierences, which are constant in 

 all the specimens examined. 



We are inclined to recognize these as the B. ovatus and B. compressus of Say, 



