296 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



As originally described Arthrotaxopsis contained four species. Two 

 of these prove to be identical with the species described below, while 

 the third was composite and included specimens of both Sphenolepis 

 hurriana (Dunker) Schenk and Sequoia ambigua Heer. 



ARTHROTAXOPSIS GRANDIS Fontaine. 



Arthrotaxopsis grandis Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 240 

 (part), pi. 114, figs. 1-3; pi. 116, figs. 1-4; pi. 135, fig. 10.— Fontaine, in 

 Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, p. 546. 



Arthrotaxopsis tenuicaulis Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 



241, pi. 114, figs: 4, 5; pi. 115, fig. 4; pi. 116, fig. 6; pi. 117, fig. 2.— Fontaine, 

 in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 516, 520, 538, 546, 571; 

 19th Ann. Rept. U. S. Geol. Surv., pt. 2, 1899, p. 674, pi. 164. 



Arthrotaxopsis pachyphyUa Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1S90, p. 



242, pi. 115, figs. 1, 3; pi. 117, figs. 1, 3-5. 



Description. — Leafy twigs elongate and slender, especially the dis- 

 tal ones, which are extremely attenuated and unbranched or some- 

 times dichotomously branched. Mam branches alternate, much 

 branched, apparently in a single plane. Distal twigs crowded, some- 

 what fastigiate. Leaves usually thin, closely appressed, elliptical to 

 rhombic hi shape, slightly keeled, acute. Phyllotaxy spiral. Cones, 

 small, ovoid, 5 mm. to 10 mm. in diameter and 1 cm. to 1.5 cm. in 

 length, made up of a small number of relatively thick, wedge-shaped, 

 peltate scales, becoming somewhat spreading with age. 



This species may be distinguished from Sphenolepis Icurriana 

 (Dunker) Schenk, with which it was confused by Professor Fontaine 

 by the method of branching and by its longer and more slender twigs 

 as well as by the usually more spreading leaves of Sphenolepis. The 

 material which constituted the species tenuicaulis and pachyphylla of 

 Fontaine is not separable from that of the type. It comes from the 

 same beds and differs merely in the condition of preservation and 

 relative positions of the twigs upon the branch. Under Arthro- 

 taxopsis grandis was also included originally certain material from 

 near Brooke, Virginia, which is referable to Sphenolepis. Both the 

 foliage and the cones are common in the Patuxent and Arundel 

 formations, and, so far as known, they do not extend above the top 

 of the latter. Very ambiguous material from the Hay Creek beds of 

 the Fuson formation in Wyoming are referred to this species by 

 Fontaine. 



Occurrence. — Patuxent formation. Dutch Gap and Fredericks- 

 burg, Virginia; Sixteenth street, District of Columbia; Springfield, 

 Fort Worthington,? Maryland. Arundel formation Tip Top (2 

 sp. ?), Arlington (1 sp.), Bay View (cones and foliage common), Mary- 

 land, Langdon, District of Columbia. 



Collections. — U. S. National Museum, Johns Hopkins University. 



