NATURAL SCIENCES OP PHILADELPHIA. 125 



marine deposits, consisting of beds of sandstone and impure lignite, wliich we 

 have regarded provisionally as of the age of No 1 of our general section. 



Lower down the Missouri, near the mouth of Little Rocky Mountain Creek, 

 this last mentioned series of rocks upon which the fresh-water deposits repose at 

 the mouth of the Judith, is clearly seen to pass beneath No. 4 of the general 

 section ; proving that Nos. 2 and 3 are not represented in that part of the coun- 

 try. As no indications were seen in this region of these latter formations, it is 

 probably they are entirely wanting towards the sources of the Missouri. 



The deposits above alluded to, (at the mouth of Judith River,) as probably on 

 a parallel with beds seen near the mouth of Big Sioux River on the Missouri, — 

 (forming No. 1, of the Nebraska section,) — are characterized, as stated in one 

 of our former papers, by a group of fossils remarkably distinct from those oc- 

 curring in any of the higher north western formations ; and there remains some 

 doubt as to whether or not they are older than Cretaceous. The presence of 

 the genus Baculites would seem to establish the fact that they belong to the 

 Cretaceous epoch ; while the occurrence in the same hand specimens with these 

 remains of Baculites, of a species of Hettangii, — a genus of bivalves, not known 

 to occur in the old world in newer formations than the Lias, — would, on the 

 other hand, indicate that these beds are older than Cretaceous. For the pre- 

 seijt, however, we express no decided opinion on this point, but content our- 

 selves with the remark, that we are inclined to think they hold a position near 

 the base of the Cretaceous system, and are probably on a parallel with the 

 Neocomien of the old world, though they may be older. 



The following section, taken near the mouth of Judith River,* will exhibit ap- 

 proximately the lithological characters, and orderof succession of these deposits 

 at that locality. It is not pretended, however, that this section represents all 

 the beds of this series, as others were observed near them, but owing to the dis- 

 tortion and disturbance of the strata, and the unfavorable circumstances under 

 which the observations were made, it was impossible to devote time enough to 

 their examination to collect the means of constructing a connected general 

 section of the whole series. We should also state here that the specimens fur- 

 nishing the data upon which this section, and that of the fresh-water and esta- 

 ary deposits near the same locality, were constructed, although collected some 

 time back, only came to hand since the communication of our last paper. 



Section op the Older Deposits at the Mouth of Judith River, in the Descbnd- 



iNG Order. 

 Bed A. — Yellowish and reddish, rather coarse grained sandstone, becoming 

 deep red on exposure, — containing Inoceramus veniricosus, Mactra alta, Car- 



dium speciosum, S(c., ^c 20 to 25 ft. 



" B. — Mixed pure and impure lignite — whole bed containing many crystals of 

 selenite, and a yellowish substance like sulphur. The masses of lignite, 

 when broken, reveal in considerable quantities small reddish crystalline 

 fragments of a substance having the taste and appearance of rosin... 6 to 8 ft. 

 " C. — Variable strata of drab clay, and gray sand and sandstone : — upper 

 part containing large numbers of Oslrea glabra. Near the middle, there are 

 gray or ash-colored clavs with very hard bluish gray granular, siliceous con- 

 cretions, containing Hcttangia Americana, Panopcea occidenlalis, Mactra for- 



mosa, <f-c., 80 to 100 ft. 



At several points near the locality where the above section was taken, the bed 

 G, of the last section, with its characteristic fossils, was seen superimposed upon 

 the bed A, of the section here given ; but the line of junction was not suffi- 

 ciently well exposed to determine very satisfactorily whether the upper part of 

 these lower deposits bears marks of denudation previous to the deposition of the 

 overlying freshwater and estuary beds or not. 



On a former occasion we expressed very briefly our views in regard to the 

 parallelism of the Cretaceous formations of Nebraska with those of New Jersey, 

 Alabama, and portions of the far west and south west. In order to make more 

 clear some of these pointj of parallelism, we here reproduce for comparison, 

 with some modifications, the general section of the Nebraska formations ; and 



1857.] 



*By Dr. Ilayden. 



