A REPORT ON THE CRETACEOUS FOSSILS CONTAINED IN THE 

 COLLECTIONS BROUGHT FROM NEW MEXICO BY THE EXPLOR- 

 ING EXPEDITION UNDER THE COMMAND OF CAPT. J. N. MA- 

 COMB, OF THE UNITED STATES TOPOGRAPHICAL ENGINEERS. 



J?y P. B. Meek. 



rhe following pages and the accompanying plates contain descriptions and illus- 

 trations of eleven new species of Cretaceous fossils. Figures and descriptions have 

 also been added of a few previously known forms, of special interest as guides in iden- 

 tifying the several formations, and in determining their relations to established horizons 

 in the same system elsewhere. 



By reference to the able report of Dr. Newberry, the geologist of the expedi- 

 tion, it will be seen thai lie divides the Cretaceous rocks of New Mexico into three 

 groups, as follows: 



1. The CJppee Division, consisting of gray, white, and purple marls, alternating 

 with soft, yellow, calcareous sandstone, altogether 1,500 feet in thickness. In this 

 £>-roup, a portion of which he thinks may possibly prove to he of Tertiary age, he 

 observed numerous silicified trunks of trees, together with leaves of Ahtus s Platanus, 

 &c. At the base of the whole, he found a thin bed containing Placenticer as placenta , f 

 Baculites anceps, var., Anchura, Tnoceramus, &c. 



2. The Middle Division is composed of dove-colored and ferruginous limestones, 

 shales, &c, altogether from l,200to 1,500 feet in thickness, and containing PHonocyclus, 

 Macombi, Scaphites Jarvmformis, Inoceramm prdblemaHcus, Osfrea congesta, &c. 



3. The Lower Division, consisting of yellow or brown sandstone and green shales, 

 250 to 400 feet in thickness, containing Ammonites, JExogyra, Plicatula, and leaves of 

 Salix, Flatanus, Quercus, &c. 



After a careful examination of the specimens from these rocks, I fully concur with 

 Dr. Newberry in the opinion that all of those of the Lower Division, with possibly 



" This report was prepared in I860, and lias remained unpublished until this time (November, 1875). I have at 

 this latter date <^i veil it as careful a revision as numerous other engagements would permit ; and, in doing this, several 



changes of nomenclature were found to he oecessarj , in order to bring the whole np to the present more, advanced state 

 of palsBontoIogical science. Such ohangesos refer to other publications issued at any date after that lirst above men- 

 tioned, were of course made in [he revision of the MS. at the latter date.— F. B. M. 



t The name l'lacoiticmis was first proposed by me in the Proceedings of tffe Philosophical Society of Philadelphia 



1870; and again need in Uayden's Second Annual Report of the United States Geological Survey of the Territories, 8SJ7, 

 1872; also in Upper Missouri Paleontology, now in the press (November, 1876). Jmmonitrs placenta, Dekay, is the type 

 of the group. 

 10 S P 



