290 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



are represented by 2 species of Sphenolepis; five species and one 

 variety of Glyptostrobus disappear altogether as does also a species of 

 Williamsonia and one of Araucarites. 



While the lack of certainty pertaining to the correct recognition 

 of coniferous foliage as ordinarily preserved in the fossil state is 

 fully recognized it is believed that the previous segregation of these 

 Potomac forms was entirely unwarranted and that the present concep- 

 tion instead of being ultra-conservative as might be deduced from 

 the synonymy still leans in the direction of recognizing too many 

 species However, it approximates at least the actual status of these 

 genera in this area during the Lower Cretaceous. 



THE GENUS SPHENOLEPIS. 



The genus Sphenolepis was proposed by Schenk in 187 1. 1 In 

 1881 Heer proposed the generic name Sphenolepidium as a substitute 

 for Sphenolepis on the ground that the latter had been previously 

 used in the animal kingdom. In his treatment of these plants in 

 Zittel's Handbuch Schenk adopts Heer s generic name which had 

 meanwhile come into general use. As, however, all modern nomen- 

 clatorial codes both botanical and zoological do not regard the use 

 of a name in one kingdom as prohibiting its use in the other, Schenk's 

 original name must stand. 



Sphenolepis may be denned as follows: Branches and twigs alter- 

 nate. Phyllotaxy spiral. Leaves decurrent, more or less imbricated, 

 acute, more or less appressed, especially on the older branches. Cones 

 small, oblong or spherical, borne on short lateral branches. Cone- 

 scales persistent, leathery, somewhat divergent at maturity, in 

 habit suggesting Sequoia. The number and position of thaseeds is 

 altogether uncertain. 



Although Solms-Laubach considers 2 that these forms can. not 

 be precisely located in any of the existing subfamilies of conifers 

 most authors refer them to the Taxodieas comparing them with the 

 existing species of Sequoia and Arihrotaxis, especially the latter, with 

 which as regards the cones, the leaf form and arrangement, and the 

 general habit there is the closest similarity, amounting almost to an 

 actual demonstration of relationship. 



The genus appears in beds of Rhaetic age both in Europe and South 

 America. In North America one species has been recorded from 

 the Oregon Jurassic, and Saporta has described a species from the 

 Upper Jurassic of Portugal. Species of this genus are widespread 

 and characteristic of the Wealden and Lower Cretaceous and con- 

 stitute a very abundant element in the flora of the Potomac group, 

 where they are represented by remains of both foliage and cones. 

 As has been frequently pointed out, the genus may be composite. 



i Schenk, Palaeontographica, vol. 19, 1871, p. 243. : Solms-Laubach, Fossil Botany, 1891, p. 71. 



