390 OLDER MESOZOIC FLORAS OF UNITED STATES. 
did not specially strike me, and I noted only that the surfaces were 
obscure in places. Through the kindness of Dr. C. E. Beecher these 
specimens were sent to me for further examination and comparison 
with those of the large collection from Professor Knight. Some of 
the important results of this comparison will be noted later on, but 
it is sufficient to state here that they form no exception or anomaly, 
but are simply part and parcel of the general lot. 
Generic characters, with the exception of Bennettites, which is 
identical with Cycadeoidea except in the accident that seeds have been 
discovered in the spadices, have generally been based on the shape of 
the trunk and on the character of the armor, i. e., of the remains of 
the foliar organs still adhering to the trunk in the fossil state. The 
former of these characters has proved of less constancy, and, in cases 
where the latter class of characters is distinctive, authors have not 
hesitated to ignore variations in the former, as, e. g., Cycadeoidea 
gigantea of Seward, a tall, cylindrical trunk, wholly different in form 
from other species of that genus. I was obliged to do the same with 
C. excelsa and C. Jenneyana. 
The second class of characters is relatively constant and diagnostic, 
and to show the differences in the different genera’ I will reproduce 
the descriptions of different authors of these generic characters, trans- 
lating where necessary: 
Bucklandia: scarred-areolate by the scars of the spadices, scales, arid petioles (Car- 
ruthers) . 
Yatesia: covered by the scales and persistent bases of the petioles (Carruthers). 
Williamsonia: scarred-areolate by the markings of the deciduous petioles (Carruth- 
ers). 
Bennettites: covered with the persistent bases of the petioles (Carruthers). 
Mantellia: same as Bennettites (Carruthers. This was Brongniart’s name of Cyca- 
deoidea, which Carruthers adopted) . 
Raumeria: densely covered or scarred by the persistent bases of the petioles and 
stipule-shaped, connate scales (Carruthers) . 
Fittonia: covered by the scales and persistent, large, geniculate bases of the petioles 
(Carruthers) . 
Crossozamia: covered by the short, subimbricate bases of the petioles (Carruthers). 
Clathraria: marked by transverse rhombic or irregularly pentagonal and hexagonal 
scars of leaves truncated above the base (Schimper). 
Cycadeoidea: enveloped by the basilar remains of the leaves, rhomboidal in cross 
section (Schimper) .? 
Bolbopodium: completely enveloped by the disjointed rhombic leaf bases of different 
lengths (Saporta). 
Cylindropodium: leaf bases short, densely crowded, with rhombic, convex scars 
(Saporta) . 
Clathropodium: leaf bases long-rhombic or elliptical in cross section (Saporta) .. 
1Many of the generic names mentioned here are of course synonyms, but have been described as 
genera. 
2 Buckland’s description was not compact. 
