WILCOX (iROIiP. 



33 



Pis. XXIII. XXXI, XXXVIII, XXXIX, aiul 

 XCII.) 



A spcH'iincn of the .so-callod seed, tube, or 

 cone gulls, coininonly |)ri)(luci'(l hy spcoies 

 of Cccidoniyiii (Dipt era) and occasionally liy 

 the Aphidida\, is shown on a ligurod leaf of 

 Ehamniis (Pi. CXI, (ig. 1). The so-callcd peti- 

 ole galls produced hy some species of Ileniip- 

 tera and more commonly liy the gall ilies 

 (llyiiienoptora) are representetl in tiui illustra- 

 tion iii Cnlrcia purtjcaren.sis (P\. LVI, fig. 2). 

 The figured leaf of Intcorea prepaniculata (PI. 

 0\'II, fig. 5) is hadly riddled in a nianuf^r 

 sugg(>sting the work of some Wilcox species of 

 leaf-cutting bee (Megachilida' of the order 

 H^Tiienoptera) . The uniformity in size of IIh^ 

 holes lends support to such an interpretation, 

 although it is possible, that these are due to a 

 brood of leaf-eating caterpillars. No traces of 

 Coleoptera have been seen, and it is also sti'ange 

 that the groups with aquatic lar\a' likc^ tlie 

 Oilonata and Ephemerida have not hU't some 

 traces of then- former presence. At any rate the 

 few obscm-e traces mentioned in the foregoing 

 paragraphs show that there could have been 

 notliing abnormal in the Wilcox insect fauna. 



With the exce]>tion of teeth of Crocodylus 

 grypus Cope, a Wasatch species, recently found 

 in Texas, no traces of vertebrates except a few 

 fish scales, as at the Piu'vear locality, have 

 been discovered. 



Poorly preserved Unios occur in the clays of 

 the Holly Springs sand or nuddle Wilcox at 

 Oxford, Miss., thus confirming the presence of 

 a WUcox estuary at this locality, indicated also 

 by the hthology. An undeterminahh^ (\>r- 

 bula( ?), a genus characteristic of shallow naariue 

 or estuary muds, is ])resent in the beds of middle 

 Wilcox (HoUy Sjirings) age near Grand Junc- 

 tion, Tenn., thus proving that the upper em- 

 bayment deposits were marginal and not con- 

 tinental in character. The poorly preserved 

 remains of a large myriapod or possibly an 

 isopod are associated with the fossil ])lants at 

 Holly Springs, Miss., and 1 i mUes west of Grand 

 Junction and at HoUy Springs and Puryear, 

 Tenn. Miss M. J. Rathbun is of the opinion that 

 these remaiiis are related to the isopotl genus 

 Ligyda Rafinesque (Ligia Fabricius) represented 

 by the common Ligi/da haudiniana, which lives 

 among driftwood and seaweed in the littoral 

 zone. Two of the best specimens are shown on 

 Plate CXI, figures 7 and 8. 



CHARACTER, SUCCESSION, AND AREAL 

 DISTRIBUTION. 



After the rhcckcred nonicnclatorial history 

 of tiu'se d(>])osits previously sketched in part, 

 geologists have agre(>d that the term Wilcox 

 group is their naost suital)le designation, as 

 they ar(> tyj)ically dcV(>loped along Alabama 

 River in Wilcox County, Ala. By typical is 

 not to !)(' understood ty|)ical in litholog\', for 

 the type of sediments of tlie upjier embaymetil 

 is much more extensive, l)ut typical in the 

 sense that the sections exposed along Alal)ania 

 and Tombig])ee rivers arc flu^ most com|)let(>, 

 covering the whole chronologic interval of 

 Wilcox sedimentatimi and sharply set off from 

 the uppermost Miilway l)elow and from llie 

 Tallahatta ])ulirstone, tlie basal formation of 

 the Clai])(>rne gi'oup, al)ov(\ 



Tiu^ Wilcox de])osits in general consist of 

 more or less extensive; lenticular beds of sands 

 and clays. The sands are commonly cross- 

 ])edd(Ml and ferruginous, and in places contain 

 clay l)alls. The clays are commonly carbona- 

 ceous and their carbonaceous matter in ])laces 

 forms consideral)lc 1)eds of lignite. 



In Alabama and along Sabine River in 

 Texas the deposits assume a marine character 

 with glauconitic sands and thin shell marls, 

 and in Louisiana calcareous concretions are not 

 un(!()nnnon. 



Both lithologic and faunal considerations 

 have suggested the segregation of the Wilcox 

 dej)ositrS in Alabama that I have termed typical 

 into the Nanafaha, Tuscahoma, Baslii, and 

 Hatchetigbee formations. 



The Nanafalia formation, termed originally 

 tlie "Coal Bluff sands and hgnites" by Smitli, 

 from the bluff of that name on Alabama River, 

 receives its name from the typical section at 

 Nanafaha Landing on Tombigbee River. It 

 consists of sandy glauconitic beds that alter- 

 nate with grayish calcareous clays, commonly 

 fossiliferous enough to be termed shell marls, 

 and that carry a large and distinctive fauna, of 

 which the small Ostrea thirsx is the most abun- 

 dant form. These marls are extensively indu- 

 rated. At the base of the formation, and imme- 

 diately a])ov(^ the Naheola formation of the 

 Midway group, occurs a bed of lignite 5 to 7 

 feet in thickness, which has been traced from 

 Pike County, Ala., westward beyond Tombig- 

 bee River, and doubtless is represented by the 



50243—16 



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