OLDER POTOMAC OF VIRGINIA AND MARYLAND. 529 



Brachyphyllum crassicaule Fontaine. 



PL CXIII, Fig. 6. 



1889. Brachyphyllum crassicaule Font. : Potomac Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 221, pi. c, fig. 4; pi. cix, figs. 1, la, lb, 2-4, 4a, 5-7; pi. ex, 

 figs. 1-.3, 3a; pi. cxi, figs. 6, 7, 7a; pi. cxii, figs. 6-8; pi. clxviii, fig. 9. 



Four specimens of B. crassicaule were found at this locality. The 

 best specimen is a distinctly defined terminal portion of a penultimate 

 twig, showing a number of entire ultimate branches. It is shown on 

 PI. CXIII, Fig. 6. It was collected on November 25, 1891. 



Celastrophyllum acutidens Fontaine. 



PI. CXIII, Figs. 7, 8. 



1889. Celastrophyllum acutidens Font.: Potomac Flora (Monogr. U. S. Geol. Surv., 



Vol. XV), p. 305, pi. clvi, figs. 8, 8a. 

 1889. Celastrophyllum ohtusidens Font.: Ibid., p. 305, pi. clvi, fig. 5. 



At the 72d Milepost in Virginia 31 specimens were found of a dico- 

 tyledon that seems to be the same with C. acutidens of the Aquia Creek 

 horizon. Nearly all the specimens are fragments of leaves that show 

 only one margin entire. The part thus presented entire, however, 

 varies in the different cases, so that an idea of the whole leaf may 

 be obtained. One specimen is a nearly entire leaf. Two species of 

 Celastrophyllum were described in Monograph XV, from the locality at 

 the 72d Milepost, ° as C. ohtusidens and C. acutidens, distinguished by 

 the greater or less acuteness of their marginal teeth. It was suggested 

 that they might be varieties of the same species, but the amount of 

 material then available was not sufficient to indicate the existence of 

 transitional forms. 



The specimens from Hosiers Bluff show gradation from the forms 

 with acute teeth to those with obtuse ones, indicating that all are varia- 

 tions of one species. The leaves with more acute teeth seem to be the 

 normal ones, hence the specific name retained should be acutidens. 



As the specimens from Rosiers Bluff are numerous, they show 

 more of the character of the leaf than could be made out from the few 

 forms obtained at the 72d Milepost. The toothing is more often subacute 



« Op. cit., p. 305, pi. clvi, figs. 5, 8. 

 MON XLVIII — 0.5 34 



