September 6, 1889.] 



SCIENCE. 



161 



The marine upper cretaceous deposits of the Atlantic coast re- 

 gion which immediately overlie the Potomac formation are best 

 developed in New Jersey ; but there is good reason to believe that 

 they were originally continuous with contemporaneous deposits 

 through the whole length of the region from Long Island to the 

 Gulf States and thence westward to, and far northward within, the 

 interior region. This opinion is based upon specific identity of 

 marine fossils discovered in the different regions. 



The upper cretaceous of this region is overlain by eocene de- 

 posits, also marine, with little if any observable unconformity where 

 they have been found in contact. I shall, however, presently men- 

 tion facts which indicate that there is in the Atlantic and Gulf 

 coast region a considerable hiatus between the cretaceous and 

 eocene. 



Briefly, then, the mesozoic of the Atlantic coast region consists 

 of a probable representation of the upper trias of Europe, a pos- 

 sible one of the upper Jura, a probable slight one of the middle 

 cretaceous, and a practically certain representation of a large part 

 of the upper cretaceous, but with an hiatus between the latter and 

 the eocene. 



Although the cretaceous rocks are, or were originally, continuous 

 between the Atlantic coast and interior regions by way of the Gulf 

 States, the earlier mesozoic rocks of those regions respectively are 

 so widely separated from each other that, as we go westward, we 

 do not find any that can be confidently referred to either the trias 

 or the Jura until we have passed the looth or perhaps the 103d 

 meridian. 



As the latter meridian coincides with the western boundary of 

 Texas, the foregoing statement implies that no triassic rocks exist 

 within at least the greater part of the fully thirty thousand square 

 miles in that State and in the Indian Territory, which some geolo- 

 gists have represented as being occupied only by rocks of that age. 

 A personal examination of a large part of that region and. of the 

 fossils collected there has satisfied me that the sum of all the 

 known evidence is in favor of the Permian age of the strata in . 

 question and against their triassic age. But these strata have an 

 important paleontological relation with the mesozoic, to which I 

 wish to call your attention for a few moments. 



Upwards of fifty species of vertebrates, embracing reptiles, ba- 

 trachians, and fishes, have been described from these rocks by Pro- 

 fessor Cope, upon the evidence of which he referred them to the 

 Permian of Europe, although, as he states, not one of the genera is 

 common to both continents. 



I have collected upward of thirty species of invertebrates from 

 the same beds which furnished the vertebrates, representative ex- 

 amples of all the more important of which were obtained from one 

 and the same stratum. Of these, fully one-half are common, char- 

 acteristic coal-measure species. A part of the cephalopod species, 

 however, possess such decided mesozoic characteristics that prob- 

 ably no special student of that class of fossil mollusca would hesi- 

 tate to refer them to a formation not older than the trias, if they 

 had been submitted to him without any information as to their true 

 stratigraphical position. 



It is a significant fact that if three special selections were made 

 from the fossils of all kinds that have been obtained from this for- 

 mation in Texas, one could be made, by the usual method of chron- 

 ological classification practised by paleontologists, to prove its coal- 

 measure age, another its Permian age, and still another its triassic 

 age. It is admitted that the sagacity of an experienced paleontol- 

 ogist will often enable him upon limited evidence to become satis- 

 fied in his own mind as to the approximate'age of a given forma- 

 tion ; but it is only after all the obtainable paleontological and 

 stratigraphical facts are carefully considered together that one is 

 justified in expressing a definite opinion upon a subject of this kind. 

 Such a summing up of all the evidence at present available seems 

 to fully justify the reference of this Texan formation to the Permian 

 of Europe. 



My special object in presenting the foregoing facts is to call 

 your attention to the important paleontological relation of the Tex- 

 an Permian with the mesozoic, which is shown by the presence of 

 ammonitic and ceratitic cephalopods among paleozoic types of 

 moUusks. The discovery of such forms in such association in the 

 Texan Permian, as well as in the Productus limestone o( India, 



shows conclusively that certain mesozoic types began their exist- 

 ence long before the close of paleozoic time. Such forms in such 

 association may be properly regarded as harbingers of an approach- 

 ing, but not yet established, mesozoic era, because, in this case at 

 least, the balance of paleontological evidence favors their reference 

 to the paleozoic. Such facts as those which have been mentioned, 

 as well as others presently to be referred to, indicate that upon the 

 confines of epochs, periods, and ages of geological time there was 

 always a commingling of types of then living forms which in their 

 culmination were characteristic of each of those chronological 

 divisions respectively. Furthermore, I shall call your attention to 

 evidence that some of the types %vhich especially characterized cer- 

 tain geological periods survived in full vigor through later periods. 

 But let us return to a consideration of the mesozoic rocks. 



Those rocks of the great interior region which have by common 

 consent, but upon comparatively slight evidence, been referred to 

 the trias, are found upturned against the flanks of the Rocky Moun- 

 tain, and other ranges, and exposed to view in the valleys and 

 caiions of the plateau province. They reach several thousand feet 

 in thickness, and are so nearly uniform in color and lithological 

 character over the whole of the great area within which they occur 

 that they are often designated as the " red beds." They are found 

 resting upon rocks of different age in different places, but in some 

 districts they rest with apparent conformity upon a series of sand- 

 stone strata which are probably of Permian age. 



This formation is apparently of non-marine origin, and, as a rule, 

 it is quite barren of fossils. The few molluscan remains that have 

 been obtained from it give no indication as to its age, and, in the 

 light of present knowledge, the few plant and vertebrate remains 

 obtained from it are far from satisfactory in this respect. Still, it 

 is not my object to deny the triassic age of this formation, but only 

 to call your attention to the fact that paleontological evidence upon 

 this point is very meagre. 



Because of the paucity of fossils both in this formation and in 

 the reputed Permian upon which it rests in different districts, little 

 is known of any paleontological relationship between them. There 

 are, however, some indications of such relationship that deserve 

 mention. The case of the commingling of mesozoic and paleozoic 

 types in the Permian of Texas has already been stated. Another 

 case in South Park, Colorado, may be mentioned, and the possible 

 occurrence of still another in south-eastern Idaho may be sug- 

 gested. 



Important collections of plants and insect remains have been ob- 

 tained from certain strata in South Park which are reported as im- 

 mediately overlying rocks of unquestionable carboniferous age. 

 The plants are regarded by Professor Ward as constituting the 

 most characteristic Permian flora that has been found on this con- 

 tinent. The stratigraphical relation of these rocks is also suggest- 

 ive of their Permian age ; and yet Mr. Scudder referred the insects 

 to the trias without qualification. 



Some years ago Dr. Peale discovered in south-eastern Idaho an 

 unique assemblage of fossils in strata which rest conformably upon 

 the carboniferous, and evidently occupy a position beneath the 

 triassic red beds, which occur in the same neighborhood. A part 

 of the species belong to the Ammoitz/zdcE and a part to the Cerati- 

 tida ; and upon the evidence of these cephalopods Professor Hyatt 

 referred the strata bearing them to the middle trias of Europe. 

 When one remembers that cephalopod forms similar to those just 

 referred to occur in India associated with a characteristic carbon- 

 iferous fauna, he naturally inquires whether it is not possible that 

 the Idaho strata ought to be referred to a period not later than the 

 Permian. 



Those Idaho strata and the South Park and Texan Permian all 

 possess great interest as indicating an intimate relationship be- 

 tween the mesozoic and the carboniferous of the interior region ; 

 and if the record between the paleozoic and the mesozoic had not 

 been so generally and so badly broken on this continent, we should 

 doubtless now find many similar and more complete cases of the 

 commingling of earlier and later types. 



Some American field geologists have privately, if not publicly, 

 expressed the opinion that the Permian ought to be assigned to 

 the mesozoic, rather than to the paleozoic ; but notwithstanding 

 the paleontological relationship that has just been mentioned, such 



