Maryland Geological Survey 233 



AcROSTiciioPTERis LONGiPENNis Fontaine 

 Plate XXIII, Figs. 1, 2 ; Plate XXIV, Pig. 7 



Acrostichopteris longipennis Fontaine, 1890, Mon. U. S. Geol. Survey, vol. 



XV, p. 107, pi. clxx, fig. 10; pi. clxxi, figs. 1, 5, 7. 

 Acrostichopteris densifolia Fontaine, 1890, IMd. (pars), pi. clxx, fig. 11; 



pi. clxxi, figs. 2, 6; pi. clxxii, fig, 13 (non pi. xciv, fig. 4 which is 



referable to A. parvifolia Font.). 

 Baieropsis foUosa Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, p. 



209, pi. xciii, figs. 4-6. 

 Baieropsis denticulata angustifolia Fontaine, 1890, Mon. U. S. Geol. Surv., 



vol. XV, 1889, p. 210, pi. cxii, fig. 7. 

 Baieropsis denticulata angustifolia Fontaine, 1906, in "Ward, Mon. U. S. 



Geol. Surv., vol. xlviii, 1905, p. 491. 

 Acrostichopteris longipennis Fontaine, 1906, in Ward, Mon. U. S. Geol. 



Surv., vol. xlviii, 1905, p. 567. 

 Acrostichopteris parvifolia Fontaine, 1906, in Ward, Mon. U. S. G^ol. 



Surv., vol. xlviii, 1905, p. 558, pi. cxvi, fig. 5. 

 Baieropsis foliosa Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., vol. 



xlviii, 1905, pp. 481, 482, 489, 504, 508, pi. ex, fig. 9. 

 Acrostichopteris longipennis Berry, 1910, Proc. U. S. Natl. Mus., vol. 



xxxviii, p. 627. 



Description. — Fl-onds with relatively long pinnse, decompound proxi- 

 mad and becoming simpler distad, the ultimate pinnules subopposite to 

 alternate, rather close set. Pinnules inequilateral and slightly decurrent, 

 cut into several narrow sublinear divisions and terminated by two or 

 more subacute teeth. The lower pinnules are wider and more laciniate, 

 and more decidedly alternate on the stout rachis. Venation fine, but 

 distinct, flabellate and dichotomous, ultimate divisions terminating in 

 the apical teeth. The sterile and smaller specimens tend to much greater 

 density than those of larger size or those showing traces of fructifications. 

 The fructifications, which are illy defined in the coarse matrix, are 

 borne on the proximal or distal or both basal segments of the pinnules; 

 the segment or segments involved becomes wider and shorter and ellip- 

 tical in outline. IsTo details can be made out. 



This species is exceedingly common in the Patapsco formation, to which 

 it is confined, being especially common in the beds of this age at Federal 

 Hill. In Virginia it occurs at a large number of localities within this 

 formation. 

 15 



