46 Transactions of the Kansas 



AUosaur us and Creosaurus, which are possibly synonymous, together with Drypto- 

 murus trihedridon, comprising probably not more than two or three species, with- 

 out much doubt included, together with Megalosaurus and Poikelopleuroii oi the 

 European Wealden, to which they are strongly allied, the most carnivorous and 

 rapacious of terrestrial reptiles kuown. The teeth are loug and sabre-like, recurved 

 and minutely serrated, and the jaws were doubtless furnished with strong 

 masseter muscles. The fore limbs were, in all, much smaller than the hinder; the 

 neck was short, the tail probably slender, and very effective as a weapon. The 

 pelvis is very imperfectly known in all the carnivorous genera, but was undoubt- 

 edl}'' very narrow, as shown by the sacrum. The astragalus was very bird-like, 

 with a high ascending proces- ; the feet three-toed. The claws were extremely slen- 

 der, curved, and pointed. The bones were all very hollow, light, and of dense 

 osseous texture. Creosaurus is estimated at thirty feet in length. They probably 

 habitually walked upon the hind feet, progressing raiher by leaping than by 

 strides. 



Caulodun and Tichosteus are very imperfectly known from teeth and fragmentary 

 vertebrte. 



That not only in species, but also in individuals, this age was very prolific, seems 

 piobable from their abundant widely scattered remains, and moreover, localities 

 but a few hundred miles apart, seem to difl'er much in their species. Not a single 

 species has been found identical in any of the three localities mentioned above, 

 although there possibly may be upon further study. Upon many obscure problems 

 of the ancient Mezozoic life, much light may be confidently expected from the 

 vast unexplored deposits of the Rocky Mountain Jura. 



CRETACEOUS FORESTS AND THEIR MIGRATIONS. 



By Prof. B. F. Mudoe, Manhattan. 



One of the most interesting problems of geology, is tlie study of the geograph- 

 ical distribution of animal and vegetable life over the globe, in the different 

 geological ages, and more particularly the migrations from one portion of the earth 

 to another, consequent on the sinking of one area beneath the ocean, and the rise 

 of another. Such changes of land have been exceedingly slow, and consequent y 

 the migrations of animal and vegetable life have been equally so. 



Prof. Asa Gray has recently, in the American Journal of Science, given us a very 

 interesting essay on tiie origin b}' migration of our present forests of America and 

 Europe. He describes the clcjse relationship of the living forests, and those fossil- 

 ized in Greenland in the Miocene deposits. From a series of facts, he comes to the 

 conclusion that the flora of both continents have descended from the common 

 stock which lived in Greenland during the Miocene epoch. He stops there and 

 goes no further back. He does not inquire from whence came the Greenland 

 forests. 



Now by the labors of Heer and others, we have a knowledge in detail of the 

 Greenland flora, not only in the Miocene, but in the Upper Cretaceous. They 

 show a near resemblance to the vegetable life of our Dakota group. As the latter 

 is much older than the former, we now propose to give our reasons for believing 



