WARD.] JURASSIC CYCADS FROM WYOMING. 897 
wood 2 to 3 cm. thick, very imperfectly differentiated into two zones, 
the inner wall, exposed in one specimen, showing large scars of the 
medullary rays, consisting of elongated alternating depressions, 10 to 
15 mm. long, 5 to 8 mm. wide, each with a raised point or cushion 
above the middle; medulla + cm. in diameter, hard, fine-grained, and 
homogeneous. 
This species consists of Nos. 500.62 and 500.76, which seem to belong 
to the same trunk, but are not exactly contiguous. They probably 
belong end to end, No. 500.62 being the upper segment and reaching 
nearly to the apex of the trunk, while No. 500.76 falls considerably 
short of reaching the base. The trunk probably had a height of about 
20cm. No. 500.62 has lost the medulla, thus exposing the inner wall 
of the woody axis as described. Both specimens are nearly covered 
without by the coating of ramentum, and the transverse fractures reveal 
its nature better than in any other specimens in thecollection. One of 
these surfaces (the upper fracture of No. 500.76) has been cut across 
and polished, and microscopic slides prepared from the region which 
most clearly shows the transition of the ramentum to the outer investi- 
ture (see Pl. LXX, Figs. 1-8). This polished surface was photo- 
graphed natural size and also enlarged four times linear, and the most 
instructive portions of the large view have been selected to illustrate 
the behavior of the ramentaceous chaff in forming the external layer. 
On account of the great interest taken by Dr. F. H. Knowlton in the 
question of the true nature of this peculiar generic character, the 
material assistance he has rendered me in preparing and examining 
microscopic slides illustrating it, and the fact that the most successful 
of these investigations haye been made on specimens of this species, I 
have thought it a proper recognition of his services that the species 
should bear his name. 
The weight of No. 500.62 is 1.22 kilograms, and that of No. 500.76 
(before cutting) 1.39 kilograms. 
Pl. XCI shows the outer surface of No. 500.62, which is completely 
encased in the ramentaceous layer, so that none of the scars are visible. 
Fig. 2 represents the inner wall of the woody zone with the scars of 
the medullary rays. Pl. XCII, Fig. 1, presents the lower transverse 
fracture of the same specimen, which shows very clearly the leaf bases 
and walls in longitudinal section overlain by the investing case of 
matted ramentum. 
Pl. XCII, Fig. 2, and Pls. XCIII to XCV, illustrate the instructive 
specimen No. 500.76, which probably belongs lower in the same trunk 
as the last. The polished surface of the upper transverse fracture, 
from which the microscopic slides were taken, is represented by Pl. 
XCII, Fig. 2. The figure is somewhat enlarged, and even here the 
origin of the ramentum from the sides of the leaf bases is distinctly 
visible withoutalens. Theline dividing the armor from the outer layer 
