FLORA OF THE SHAt^TA FORMATION. 247 



with reference to the midril). Those lowest down stand at a lai-ge anjjle; 

 it may be a right angle. The nearer yoii approach tlic end of the leaf 

 the more obliciue are the leaflets, and at the end they stand in the pro- 

 longation of the midril). I regard the mode of attachment of the leaflets 

 to the midril) as the most important, and it certainly is the ~niost 

 nnvai'ving, featnre (jf this {)lant. The leaflets ai'c attached, not on the 

 face of the midrib, bnt to the side in the plane of its npper face. The 

 epidermis of the leaflet is continuons with that of th(> midrib. So far 

 are the leaflets from being articulated witli the midrib that they are 

 remarkabh' persistent. They are narrowed toward their bases, l)ut not 

 at them, and there is no abrupt rounding off at the base as in Zamites, 

 but they are decurrent along the midrib. The terminal leaflets are 

 always decidedly narrower than those lower down on tlie midiib and, 

 as before stated, are much more obliquely placed. 



Nathorst, in describing specimens of this species olitained fi-om 

 Japan, has proposed Zamioph^dlum as the generic name for it." He 

 objects to the name Dioonites for this plant because it is unlike Dion in 

 having its leaflets narrowed toward the base and in having them obliquely 

 placed. He states further that he thinks it not impossible that the 

 plant now in question may belong to the li\'ing genus Zamia. The first 

 objection is the only one that holds good, for, as has been stated, the 

 second is not applicable to the leaflets in the lower portion of the leaf, 

 and, in any case, such a feature can have no great value. Perhaps it 

 would have been better in the original determination of the plant to have 

 placed it in a new genus, but it does not seem fitting to rename it with 

 such a generic appellation as Zamiophyllum. This suggests an affinity 

 with Zamia, of which there is no evidence. It diit'ers from Zamia in the 

 absence of articulation of the leaflets and in their marked persistence on 

 the midrib. Besides, the basal portions of the leaflets differ in form 

 from those of Zamia. Seward, as before stated, describes a number of 

 fine forms that he identifies with Dioonites Bucliiamis.'' He includes 

 these plants in the genus Zamites, modifying the generic description 

 somewhat. His figures and descriptions make it plain that his fossils 

 are different from the Potomac forms described by me as Dioonites 



1 Beitriigc zur Mesozoisclien Flora .Tapans, pp. 6, 7 (see synonymy, p. 245). 

 6 Fossil Plants of the Weaklcn, Part II, pp. 7.T-8G. 



