Maryland Geological Survey 365 



which gives ofl at nearly right angles rather remote, short, simple 

 secondary veins, which run direct to the margin. 



This genus is based on the forms which Professor Fontaine referred 

 to Sequoia and which he compared with Cycadites and certain existing 

 species of Podocarpus as well as with the Triassic Taxites falcatiis of 

 N"athorst. 



The distichous phyllotaxy is decidedly against the reference of these 

 forms to the Coniferales, for while many conifers have a distichous 

 habit the phyllotaxy is cyclic or spiral. The attachment of the pinnules 

 is also against a reference to the Coniferales, as is also the venation. 

 The dichotomous frond-habit, while wanting in modern cycads, is in a 

 measure paralleled by the bipinnate fronds of Bowenia and by numerous 

 bipinnate Mesozoic cycadophytes. Finally in a group derived from the 

 Paleozoic pteridosperms, the majority of which had highly decompound 

 fronds, some of which like Odontopteris, which is probably a member 

 of this phylum, had a dichotomous habit (cf. Odontopteris minor 

 Brongniart), it would be more than anomalous if all of the Mesozoic 

 forms had the foliar characters of the modern cycads and none retained 

 any of the foliar characters of their Paleozoic ancestors. 



DiCHOTOZAMiTES CYCADOPSis (Fontaine) 

 Plate LXXVII, Figs. 2, 3 



Sequoia cycadopsis Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 



p. 243, pi. cxii, figs. 9-11; pi. c^iii, figs. 1-3. 

 Sequoia cycadopsis Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., vol. 



xlviii, 1905, pp. 489, 533, pi. cix, fig. 11. 



Description. — Frond dichotomously compound with a slender keeled 

 rachis. Pinnules slender, linear, acuminate, markedly decurrent, slightly 

 curved. They are attached to the rachis laterally and are ascending, sub- 

 tending an angle of about 22°. Length variable, averaging about 3 cm. 

 The length and angle vary with the position on the frond and the arrange- 

 ment is rather open and varies from alternate to opposite. 



Each pinnule has a midvein which is prominent below and sunken 

 above. Secondaries branch from it at an angle of nearlv 90°, and are 



