MIDWAY FORMATION. 



9 



Mississippi miuI Cache Rivor bottoms or cov- 

 crod witii ]M('ist(U'i'ii(> deposits west of tlie 

 Illinois area, altiioiigii Sliepard idenlilies it in 

 at least one well in southeastern Missouii. Tlie 

 Midway deposits reappear in Independence 

 County, Ark., from wliicii locality they may be 

 traced southwestward with hut few lireaks. In 

 the vicinity of Little Kock tlu> Midway, wliich 

 fiiere consists of calcareous sands and fossilil'er- 

 ous limestones, (iv(>rlaps tlie Cretaceous and 

 rests on tlu^ Paleozoic. 



The Midway is extensively developed from 

 Arkansas southwest\\ar<l across Texas to th(^ 

 Rio Cii'ande. I'sually it iuis not yet been sub- 

 divided aiul tlu^ name is used in a foruuitional 

 ratlier than a group sense, althouj^h the tiuck- 

 nesses indicate the presence of deposits laid 

 down during the tinu' interval represented by 

 the typical Midway of Alabam;i. In the 

 Texas area the Midway consists of 200 to 400 

 feet of lignitic clays and sanils with fossilif(>rous 

 concretions. According to l)und)le ' if ex- 

 tends an undetermined distance into Mexico. 



There is an erosional miconfornuty at the 

 base from Georgia to the Kio Grande, although 

 it is largely obscured by the lithologic similarity 

 between the U]^per Cretaceous and tlie basal 

 Eocene. 



LOCAL SECTIONS. 



As has been already stated, the Midway in 

 its tj'pe area contains few if an}^ determinable 

 plant remains, altliough lignitic inclusions are 

 widespread and carl)onaccous clays and less 

 finely divided remains of former vegetation 

 testify to the nearness of .shores covered with a 

 luxuriant plant growth. All the determinable 

 Midway ( ?) plants have conu^ from a single 

 outcrop near Earle, in Bexar County, Tex., 

 and only two local sections are here presented. 



At Earle," about 11 miles du(? south of San 

 Antonio, in a guUy just south of Medina River, 

 a hard calcareous sandstone carrying fossil 

 leaves has been quarried. This rock is the 

 indurated portion of a greenish-gray cross- 

 bedded, rather line sand formation. The 

 whole thickness is exposed for more than 40 

 feet, but the country is flat and exposures are 

 rare and disconnected. iVlong Medina River, 

 about o\ miles west of the leaf-bearing out- 

 crop, at a slightly lower stratigraphic horizon, 



' Dumble, E. T., Science, new .ser., vol. Xi, pp. 232-2:!l, 1«11. 

 - 1 am indebted to L. W. Stephenson and Alexander I>eussen for col- 

 lections and notes on this locality. 



Deussen has collected Midway invertebrates, 

 ;ind in his opinion tlierc is little >loubt of tlu^ 

 Midway age of the plant-bearing bed at Earle. 

 Tiie otdy other section of de|)osits of Midway 

 age wortii mentioning in I lie present comiection 

 is idong the Soutliern Railway _' miles (\isl of 

 Middlclon, in Hardeman County, Temi. \\ 

 tliis locality a low exposure in the Po/tcrs 

 Creek clay shows about 10 feet of yellowisli 

 weatliered, slightly glauconitic sand, grading 

 down into ti frial)le sandy micaceous di'ab clay 

 with ferruginous lilms, thtit carries botli broken 

 Iciives and casts of invertebrtites. The dral) 

 clay is exposed for about 4 ftn-t. None of the 

 leaves are specifically determinable, but at least 

 two s])ecies of I'^icus and sevend other genera 

 are re])resented. .Vboiil half a mile west of this 

 outcrop ii siindy micaceous glauconitic clay of 

 tlu^ same :ige conttuns a considerable Midway 

 faima. 



RELATIONS OF THE FLORA. 



The flora thus far found in Midway deposits 

 is so extremely scanty that it affords little 

 basis for (>xtcndcd comparisons with other 

 floras of about the same age or those im- 

 mcdiattdy older and younger. However, as 

 the protiability of the discovery of extensive 

 |)lant-bearing deposits of Midway age in the 

 future is slight, certain conclusions may be 

 deduced from the present collections. Only 

 10 species are described in the systematic 

 section devoted to this flora, all leaves of 

 dicotyledont)Us plants, including representa- 

 tives of the families Moracejp, Platanacea>, 

 Lauracea\ Anoiuu-ca', Papilionacea> and Com- 

 liretacca'. Tlie family Moracea? is the most 

 abundant , four species and fragments of other 

 unidt'iitiliable f(_>rms having been obtained at 

 different localities. When comparisons are 

 made with the immediiitely antecedent flortis 

 of the Upper (^retaceous in this and other 

 areas a very great discontinuity is at once 

 apparent, in spite of the smallness of the known 

 Midway (0 flora. 



The areal distribution of the Upper Cretace- 

 ous (lc])osits of southeastern North Anu'i'ica 

 has been studied in detail during the last six or 

 seven years by Mr. L. W, Stephenson, who is 

 an experienced and assiduous collector of fossil 

 plants. I have also been over most of the 

 area, so that the failure to discover fossil plants 

 can not be attributed to th(> lack of careful and 



