874 Bibliographical Notice, 



the Green River Valley down the Colorado into New Mexico, where 

 they have been noticed and described by various explorers. These 

 beds have usually been correlated with the European Trias ; and the 

 fossil plants found in them by Dr. Newberry in New Mexico appear 

 to favour that idea ; but Dr. Hayden does not feel confident on the 

 subject, especially as he says, " On the west side of the Wind River 

 Mountains we have discovered fossils beneath the red beds, which 

 may include those in the Jurassic" (p. 123). 



VI. " The Jurassic rocks are everywhere revealed overlying the 

 red deposits just mentioned, and possess an equal geographical ex- 

 tension." Around the Black Hills and along the flanks of the 

 Rocky Mountains, they are upheaved in a zone from a quarter to 

 three miles wide, and consist of, — 1st (lowest). Laminated sandstones 

 and shales, with Trigonia, Pecten, Mytilus, Serpula, Avicula (Mo- 

 notis) tenuicostata, Meek & Hayden, Pentacrinus astericus, M.&H., 

 Lingula brevirostra, &c, 60 to 100 feet. 2nd. Marls, 30 to 40 feet. 

 3rd. Sandstones and marls, with Area inornata, Panopcea (Myacites) 

 subelliptica, M. & H., Avicula tenuicostata, Ostrea, Hettangia, 

 Ammonites cordiformis, M. & H., A. Henryi, and Belemnites densus, 

 M. &H.; and a calcareous grit, of freshwater origin [Wealden ?], 

 with Unio nucalis, Planorbis, and Paludina (?), altogether 50 to 80 

 feet (p. 42 & p. 123). These Jurassic strata are not the so-called 

 " Jurassic " of Marcou. 



VII. The Cretaceous system "holds a very important position in 

 the North-west, not only from the vast area which it occupies, but 

 also from the number, variety, and beauty of its organic remains." 

 It is divisible into five members. The lowest, No. 1, "is a well- 

 marked and distinct division along the Missouri River from De Soto 

 to a point above the mouth of the Big Sioux River in the eastern 

 portions of Kansas and Nebraska, and in the south and south-west." 

 Towards the north-west it seems to merge into No. 2 division. No. 1 

 is an important group of beds, sandy and argillaceous, about 200 feet 

 thick in Nebraska, and containing lignite, fossil wood, impressions of 

 Dicotyledonous leaves, Equisetum (?), Pectunculus Siouxensis, H. & 

 M., &c. 



At the mouth of the Judith River, the beds referred to the Creta- 

 ceous groups Nos. 1 & 2 are from 1500 to 2000 feet thick, and con- 

 tain lignite, Credneria, Inoceramus pertenuis, Mactra alta, Cardium 

 speciosum, Meretrix Owenana, Thracia subtortuosa, Ostrea glabra, 

 Hettangia Americana, Panopcea occidentalis, and Mactra formosa ; 

 also freshwater beds [Wealden?], with Lepidotus, Uniones, Melanice, 

 Cyclas, and Helix (pp. 72, 125, 133). 



The thick red sandstones of group No. 1 afford lofty vertical bluffs 

 in the Valley of the Elkhorn, which the Indians have sculptured with 

 hieroglyphics. Blackbird Hill, on the Missouri, is a typical locality 

 for this leaf-bearing Lower Cretaceous group, which here underlies a 

 soft whitish limestone containing Inoceramus problematicus and fish- 

 remains (group No. 3?, p. 10); on the Elkhorn it is overlain by 

 group No. 3 (p. 71) ; and elsewhere, though sometimes hidden and 

 sometimes apparently wanting, it seems usually to hold a definite 



