44 Transactions of the Kansas 



the marine beds coniainiui^ an abundance of characteristic Jurassic invertebrates. 

 The bluish clayey shales here preponderate, but are variously interspersed with 

 admixtures of clay and s lud, soft and hard sandstones, in all of which fossils are 

 found, in some cases even large bones being imbedded, partly in sandstone, partly 

 in shale. Invertebrate fossils ai'e extremely rare. Of the vertebrates the individ- 

 uals most numerously represented are the tortoises, {Compsemys) with not infre- 

 quent teeth of Ceratodus, and verlebne probably of the same. Of isolated teeth, 

 those most frequently met with pertain to the crocodiles and carnivorous dinosaurs. 

 Isolated bones of single individuals of the larger species are occasionally found, 

 but not in a single instance do I know of numerous bones, pertaining to one 

 skeleton of such species, being found unmixed with other remains. By far the 

 most commonly, extensive deposits, or "quarries,' are found containing remains 

 of numerous individuals mingled together in the most inextricable confusion, 

 and in every conceivable position, with connected limb bones standing nearly up- 

 right, connected vertebrae describing vertical curves, etc., precisely as though in 

 some ancient mud holes these huge monsters had become mired and died, and suc- 

 ceeding generations had trodden their bones down, and then left their own to 

 mingle with them. Such extreme confusion is however only seen in the clay de- 

 posits containing fewer waterworn fragments and small animals. 



In sandstone deposits the large bones, though variously intermingled, are 

 generally lying more nearly horizontal, with abundant waterworn fragments, 

 and numerous remains of turtles, crocodiles, fishes, and small saurians. 



These beds have hitherto been classified as the lower or Dakota group of the 

 cretaceous, and still are by Prof. Cope. That no marked line will be found .separat- 

 ing these estuary deposits from the Dakota, as defined by the distinguished paleon- 

 tologist, Prof. Lesquereux, is possible, but until better evidence is obtained among 

 the iuvertebratesto unite them, it will be far more reasonable to accept the evidence 

 of the vertebrates, and assign to them, as Prof. Marsh has done, an equivalency with 

 the European Wealden or Upper Jurassic. 



So far, in addition to the dinosaurs, (me species each, of fish, tortoise, crocodile, 

 {JJiplosuurns Msh.) plerodacLyl, (P. montdnus Msh.) and mammal {Dri/ol'stes priscas 

 Msh.) have been described from this formation. Of the dinosauria, so far thirteen 

 genera have been characterized by Profs. Marsh and Cope, as follows : Titanosau- 

 rus Msh, (Atlantaurus Msh), >S/egosa'iru.s, Msh, Nanosaiin/s Msh, Camerasau- 

 rus Cope; Apatosdtirus Msh, Allosaun/s Msh, Caulodon Cope, TichosteuH Cope, 

 Amphicoelias Cope, Murosaurus'K&h, Creoi-aurusM^h, LaoatmrtiK Msh, and Diphdo- 

 cus, Msh, and of which probably one-half are synonyms. Titanoxnurus and Catn- 

 erasaurus are without much doubt synonymous, and the latter is considered by 

 Prof. Owen identical with his Chondrosteomurus, which is, however, only known 

 from two imperfect vertebra? from the English Wealden. The same evidence 

 would however include ^P'<ioAv<«/7/« and Moros(iur>iH,'b\x\, among these there are 

 certainly two valid genera, as proved by the structure of the pelvic girdle, and 

 hence, till the original type of Chondrasteo^iaurua is better known, it will be pre- 

 mature to unite the American species with it. According to the rules of Zoological 

 nomenclature, no genits is entitled to acceptance, unless it is distinctively charac- 

 terized. But so long as it is the custom to define genera from single bones, or un- 

 characteristic parts of the skeleton, such a rule has its objections. If, as in the pres- 

 ent case, several genera, which can not be individually separated from the original 

 imperfect type, are successively eliminated, the last must assume the type name ; 

 but this original genus may be found, when better known, to be distinct from any of 

 them, or perhaps identical with some other one previously eliminated. Or, perhaps 



