440 Systematic Paleontology 



ArtJirotaxopsis expansa Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., 

 vol. xlviii, 1905, pp. 504, 520, 546, 571 (non pp. 533, 535, 538, 555, 573, 

 pi. cix, figs, 12, 13 wliicli are referred to Seqtwia amhigua Heer, and 

 p. 547 wMcli is referred to Widdringtonites ramosus (Font.) Berry). 



Glyptostrodus expansus "Ward, 1906, Mon. U. S. Geol. Surv., vol. xlviii, 1905, 

 p. 543. 



Sphenolepidium Sternbergianum densifoUum Fontaine, 1906, in "Ward, Mon. 

 U. S. Geol. Surv., vol. xlviii, 1905, p. 524 (pars), pi. cxii, fig. 11 (non 

 figs, 1, 10), 



Glyptostrohus 'broo'kensis Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv,, 

 vol. xlviii, 1905, pp. 483, 486, 520 (non other citations). 



ArtJirotaxopsis expansa Berry, 1911, Proc. U. S. Natl. Mus., vol. xl, p. 297. 



Description. — Branches and twigs elongated and extremel}^ slender, 

 widely spreading and sparingly branched, showing a tendency as pre- 

 served to be in a single plane altliongh it cannot be determined to what 

 extent this reflects the original habit of the plant. Leaves spirally 

 arranged, thick, keeled, acute, showing a tendency to become obtuse and 

 less appressed, especially on the older twigs. 



As here delimited this species is confined to the older Potomac 

 although it is very similar to those forms from the Patapsco formation 

 which are described as Widdringtonites ramosus (Fontaine) Berry, the 

 latter being more copiously branched, less spreading, and with more 

 acute leaves which frequently become more or less elongated. These 

 differences may or may not be of specific value. As preserved the two 

 plants differ decidedly in aspect but this is due largely to the spreading 

 habit of the present species, and is approached in some of the coniferous 

 twigs from Mt, Vernon which are referred to Widdringtonites. 



The relation to Arthrotaxis implied by the name is not certain and 

 the present species is retained in the genus to which it was referred 

 by Professor Fontaine, more from a desire to avoid changes which do 

 not appear to be justified by the meager evidence at hand than from 

 any conviction of relationship. For the same reason it was not trans- 

 ferred to Widdringtonites although it seemed desirable in the case of 

 Widdringtonites ramosus to make such a change and bring the latter 

 in association with the Upper Cretaceous species of that genus with 

 which there is such a close agreement. 



