O. C. Marsh — Footprints of Jurassic Dinosaurs. 229 



The Cycad beds, as they may be termed, from the great 

 number and variety of remains of this group of fossil plants, 

 are abundantly represented around the rim of the Black 

 Hills, apparently at a higher level, but, as the Cycad remains, 

 although distinctive in themselves, have not yet been found 

 absolutely in place in undisturbed strata, their exact position 

 in the series cannot at present be definitely fixed. Fart of 

 this series was formerly referred to the Dakota by various 

 geologists, but this reference is fairly open to question, as the 

 writer has shown elsewhere.* 



c* 

 o 



o 



O 



Recent. 

 Quaternary. 





Tapir, Peccary, Bison. 



Bos, Equus, Tapir us, Dicotyles, Megatherium, Mylodon. 



6 



.2 



1 



Pliocene. 



Equus Beds. 

 Phohippus Beds. 



Equus, Tapirus, Elephas. . 



5 Pliohippus, Tapiravus, Mastodon, Procamelus, 



I Aceratherium, Bos, Morotherium, Platygonus. 



Miocene. 



Protoceras Beds. 

 Oreodon Beds. 

 BrontotheriumBeds 



Protoceras, Miohippus, Diceratherium, Thinohyus. 

 5 Oreodon, Eporeodon, Hycenodo?i, Ictops, Hyraco- 

 1 don, Agriochoerus, Golodon, Leptochoerus. 

 5 Bronlotheriurn, Brontops, Allops, Titanops, Titano- 

 \ therium, Mesohippus, Ancodus, Entelodon. 



6 

 o 



C 



Cretaceous. 



Ceratops Beds of 

 Laramie Series. 



Ceratops, Triceratops, Claosaurus, Ornithomimus. 

 Mammals, Cimolomys, Dipriodon, Selenacodon, 

 Nanomyops, Stagodon. Birds, Cimolopteryx. 



Atlantochelys Beds 

 of Montana Group. 



Atlantochelys, Coniornis. 





Pteranodon Beds of 

 Colorado Series. 



Mosasaurs, Edestosaurus, Lestosaurus, Tylosaurus. 

 Pterodactyls, Flesiosaurs, Turtles. 



Jurassic. 



Cycad Beds. 

 AtlantosaurusBeds. 

 Baptanodon Beds. 



Cycad s, Cycadeoidea. 



Dinosaurs, Barosaurus, Brontosaurus, Morosaurus, 



Diplodocus, Stegosaurus, Camptosaurus, Allo- 



saurus. Mammals, Dryolestes, Stylacodon, Tinodon, 



Ctenacodon. 

 Baptanodon, Pantosaurus, Belemnites, Trigonia, 



Pentacrinus. 



Triassic. 



Red Beds. 



A few plants. 



Geological Horizons above Paleozoic of Black Hills Region. 



Well-marked Cretaceous strata, showing the characteristic 

 yellow chalk of the Pteranodon beds of the Colorado series, are 

 developed east of the Black Hills, and contain an abundance 

 of characteristic fossils. These deposits the writer personally 

 explored in 1889, and proved their identity with the well- 

 known series along the Smoky Hill River in Kansas. 



Next above come the Atlantochelys beds of the Montana 

 group, well developed, and marked by remains of gigantic 

 turtles, as well as by characteristic mollusca, and other inverte- 

 brates. The top of the Cretaceous east of the Black Hills is 

 formed mainly by this group. On the western side of the 

 Hills, the highest Mesozoic deposits are the Ceratops beds of the 

 Laramie. These form one of the best-marked horizons known 

 in any country, as here occur the gigantic horned Dinosaurs of 

 the genus Triceratops and others, as well as numerous small 

 Cretaceous mammals and birds. 



*This Journal, vol. vi, pp. 107, 115, and 197, August, 1898. See also, the 

 present number, p. 219. 



