262 



FOSSIL PLANTS FROM TEXAS FONTAINE. 



iievov ftivo, so concct an idea of tlio llora ofllie tiiiu' as iliose tliat are 

 entonibed wliero tlu'y Irll. It is <;r«'atly to l»c dcsirt'd tlial near sliore 

 Ibiinations of tlie epoch now in (iiiestion containini;' fossil ]»laiits may 

 be (liscoviM'ed. In that case the a])senc(^ of types in the fossils wonld 

 more ]»rol)al>ly indicate their absence in tlie tlora. 



Whih^. the conditions under which they were ])reserved indicate that 

 the Glen Rose fossils i)robably ''■ive ns a very imperfect idea of the 

 flora of the tiin(^, th(^ amount of material obtained is not hirjjje enon**!! 

 to give us much conlidence in any negative eonchisions (concerning' the 

 character of the Trinity llora. To tliis must be added tliefa<tttliat the 

 ])lants are obtained from a single very small area in all the vast ex- 

 panse of the Trinity beds. The collection was contained in live quite 

 small boxes. The greater part of the material is in the form of dnpli- 

 cates of a few tyi)es, and this shows that Mi-. TTarvey obtain«'d as fnll 

 a representation as was possible of the forms found at the locality. 



i'rof. Robert T. Ilill, of the U. S. Geological Survey, established the 

 snbdivisions of the Lower Cretaceous of Texas now generally ac(;e]>ted, 

 after determining the true order of succession of the fornmticms of that 

 great state. lie gives for the Lower Cretaceous the following grou|)ings, 

 the Comanche series forming the base of the Cretaceons: 



('oiiiunche St-rirs. 



in. AVashita Division 



[ 10. IViiisoii beds. 



) !». Fort WoiMi beds. 



\ S. DiK k Creek beds. 



[ 7. Sehloeiil)acliia l)eds. 



(!. ('a)iriiia. limestone, 

 .">. (loniancbe I'eak l<eds. 



II. Coinauehe I'eak or 



Fiedricksbura; Divis- ,<,.-, , . 



'^ 1 4. W ahuit- elavs. 



ion. o 1) 1 1 



(^ 3. I'aiuxy sands. 



, rr • -i T»- • • S 2. Olen Kosc or alternatintj: beds. 



1. I iinity Division. , ^ i> i 'i' ■ •< i 



•' ( 1. I>asal I riiiity sands. 



In a letter to the writer, Trof, Ilill states that the Glen Itose fossil 

 plants occur in a lenticular mass of tine sediment, in a chalky lime 

 nmss full of marine ibssils, about 250 feet above the bottom of the 

 Trinity Division. According to him, there is no break between the 

 basal Trinity sands and theClhui 1{<>S(^ beds. The latter ie))resent <le- 

 posits laid down in deeix'r Maters farther from land. The Trinity ba- 

 sal sands were formed as the sea advanced IVom its ])resent outline 

 across the whole state of Texas. 



Attention may here be called to the similarity in the (conditions at 

 tending the formation of the Trinity beds and the Potomac beds, as 

 found in A'irginia, which latter hold a fossil tlora nearly allied, in its 

 older elements, to that of the Trinity. The Potomac beds of Virginia 

 (the lower l*otonuic) (contain the fossil ])hints in lenticular beds of clay 

 which lie in the sands and other coarse materials, the clay beds rei)re- 

 senting eddies in the uncpiict wateis. Tln^ Virginia Potonmc sands 

 and gravels wei'(^ laid down in shallow sliore waters, in a |>rogressing 

 subsidence. But in tlu' case of the Virgiiiiabeds we ha\<' no evidence 

 that the subsidence was sulticicnt (o i»roduce limestone. 



