FLORA OF THE SHASTA FORMATION. 249 



different subgenera. Sewai'd's plants are evidently a quite different 

 t^ype from these. Nathorst's Zamiophyllum Naumanni, found in the 

 same Japanese formation as the specimens of Dioonites Buchianus, 

 which he names Zamiophyllum Buchianum, is a species of the same type 

 as Seward's forms. It is probably specifically different from the latter. 

 Nathorst's Zamiophyllum Buchianum and the original Pterophyllum 

 Buchianum of Ettingshausen are, in my opinion, the same species as the 

 Potomac plant. For these I prefer to retain the name Dioonites Buchi- 

 anus. That name is established, and the genus is as near Dion as Zamia. 

 Perhaps it would be well to make a new genus for the plants with leaflets 

 inserted on the upper face of the midrib, like those of Seward, in order 

 not further to extend the application of Zamites. This new genus 

 might be called Zamiophyllum, as Nathorst proposed. 



I think that some of the confusion that has arisen in the classifi- 

 cation of cycads, based partly on the mode of insertion of the leaflets, 

 comes from the fact that authorities have not used the descriptions 

 "attached to the upper face of the midrib" and "attached on the upper 

 face" always in the same sense. It ma}^ be meant, in the case of the 

 former, that the leaflets are attached, not on the upper face and within 

 its margin, as in the case of Seward's plants, but to the sides of it, so as 

 to be in the same plane with the upper face of the midrib, as is true of 

 Dioonites Buchianus. Certainly it is verj^ desirable that there should be 

 a thorough revision of the classification of the fossil cycads that are 

 known only by their leaves. In Monograph XV of the United States 

 Geological Survey, page 181, speaking of Bornemann's genus Dioonites," 

 as characterized by Schimper, I made the latter say that the leaflets 

 are "sometimes expanded at base so as to extend up and down the rachis." 

 This was a translation of Schimper's words "basique leniter pro- et 

 decurrentibus," which he used in his synopsis of the character of Dioonites-, 

 given on page 128, Vol. II, of his Traite. It escaped my notice that on 

 page 147 of the same volume, in giving again the character of this genus, 

 he uses different words, viz, "e basi anguste decurrente, hand angustata.'"' 



" The genus Dioonites was named and described by Miquel in 1851 (Over de Rangschikking der fossiele 

 Cycadese; Tijdschr. v. d. Wis-en Naturk. Wetensch., Deel IV, Amsterdam, 1851, p. 211 [7]), and is so 

 credited by Bornemann. Miquel did not refer Ettingshausen 's Pterophyllum Buchianum to this genus. It 

 was named from its resemblance to Lindle3''s living genus Dion, wrongty spelled Dioon by many authors. — 

 L. F. W. 



^Miquel's language for this character is as follows: "inferne retrorsum subdecurrentia." — L. F. W. 



