OLDEK POTOMAC OF VIH(J1M.\ AND MAHVLAND. :)T'.> 



latter idcntiticd throo .species. Two of them, Sajuaia (unhii/iui Heec and 

 S. Heichoiharlii ((!ein.) Heer, are important fos.sils in the Lower Potomac 

 of A'irginia. Tlie ihiid is identical with a fossil desci'ilxMl by me fi'om 

 the (den Uose \hh\s of the 'i'l'iiiity of Texas, with the n;iinc I'diiidjilijilhuii 

 Ciubiuni." This hitter |)iaii1 Doctoi' X;itlioi-st named J'.s('U<l()i'reiicl()j>><i,s 

 Feli.ri, and in descrihiiif!!; it he made some ei'i'ors whicli, as they may lead 

 to further errors and confusion, are noticed below. 



These facts seem to indicate that a Xeocomian or Lowim- Cretaceous 

 age ma}' be claimed with ;i j^ood deal of confidence for th(> Towei- Potomac 

 flora. 



So far as T am informed, the only evidence claimed to opi)ose the 

 conclusion that these l)e(ls are Low'er ('retaceous is that jji'esented by 

 Profes.soi' Marsh, which was derived from an examination of llie vei'te- 

 brate fauna of the Arundel group and the Como beds. This, howevei-, 

 simply goes to indicate the \\'e;d(l<'ti age of the sti;ita. 



When Doctor Xalhoi'st made his detcMinination of the Mexican 

 plants for Doctor I'Vlix he had not seen the paper on the Texas (lien 

 Rose fossils })repared Ijy me, and when his paper was prepared Doctor 

 Xathorst's article had not been read by him. The result was that the 

 same species was described under two different names. However, Doctor 

 Nathorst liad Ix^foi-e him my description of Frcnclopsis /xirccrdn/o.sft given 

 in Monograi:)h XV. Frcmi certain similarities in the Virginia and Mexican 

 fossil Doctor Xathorst concluded that they are the same. From the 

 study oi the Mexican plant he decided that the Virginia fossil had been 

 incorreetl}' diagnosed. Hence he formed a new genus, which he calls 

 Pseudofrenelopsis. Had Doctor Nathorst possessed specimens of Frene- 

 lopsis parceramosa he would never have fallen into this error. The 

 plants are quite different and prol3a!)ly are not nearly allied. The Texas 

 plant, which is that described by Doctor Nathorst, does not have jointed 

 branches. Doctor Nathorst assumes that I incorrcM-tly diagnosed 

 Frenelopsis pareernmosa as having jointed twigs. Ther(> is not the 

 shadow of a doubt that it has. F. parceramosa has its branches con- 

 spicuoush^ constricted at the joints, and the latter are so marked that tlu^ 

 branches break up into small fragments by a sej)aration at the joints. 

 Hence it is difiicult to get a twig of any considei'able length. 



"Fontaine, Notes on .some fossil plants from the Trinity division of the ('omiinijie series of Texas: Pioe. 

 U. S. Nat. Mus., Vol. XVI, l,sy.3, pp. 271-27:5, pi. x.\.\i.\, ligs. 2-11. 



