250 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



Locality: Entrance to Trent's Reach; only one specimen found. 



This peculiar plant differs from most Araucarias in several features. 

 On the upper face of the stems scars appear, as if formed by the removal 

 of leaves, indicating that they were arranged in four rows. It is possible 

 that the leaves on the upper and lower faces of the twigs were different 

 from the lateral ones and smaller. The top of the twig shows what seems 

 to be a growing bud of undeveloped leaves, and it indicates that the leaves 

 were really spirally arranged, but by twisting of the bases or footstalks 

 were brought into the same plane, grouping themselves in four rows. The 

 nerves were obscure. 



Araucaria zamioides, sp. nov. 



Plate CXXI, Fig. 1. 



Leafy ultimate twigs terminating with a leaflet like those lower on the 

 twig ; stem slender ; leaves closely placed, alternate, pinnately arranged in 

 the same plane, flat, thin, slightly falcate, widest near the base and nar- 

 rowing gradually to the tips, which are acute, attached by a slightly 

 twisted base ; nerves several, parallel, and ending as in Zamia, partly on 

 the margins near the tips, quite slender and inconspicuous. 



Locality : Hill-side near Potomac Run ; very rare. 



This plant is a good deal like a cycad of the Pterophyllum type. 



TAXODIUM Richard (GLYPTOSTROBUS End).) 



The fossils of the Potomac flora belonging to Taxodium are found in 

 the group of plants united by Endlicher in the genus Gli/ptostrohus, which 

 genus is now by Bentham and Hooker placed with Taxodium. Schenk* 

 says of Glyptostrobus, that the leaves are attached spirally and are of 

 various shapes; "they are either upright, short, appressed, oval, acute, 

 scale-shaped, the tips on the older stems not seldom divergent, or else on 

 the horizontal twigs arranged distichously, linear acute. On upright stems 

 these also are directed upwards. Both kinds of leaves have decurrent 

 bases. * * * Ripened cones, woody, oboval in shape, with scales wedge- 



' Zittel's Handbuoh der Palieontologie, vol. 2, p. 295. 



