FOSSIL CYCADEAN TRUNKS FROM WYOMING 267 



500.26 may be a lower segment of the same trunk, but if so it must 

 have been contracted at the base, as is the case with No. 500.3. Nos. 

 500. 8 and 500.67 fit each other and the former, which was shattered 

 when received, has come in three pieces. It represents a section be- 

 tween two oblique but chiefly vertical fractures. No. 500.52, a thick 

 somewhat cubical piece, almost certainly belongs to No. 500.8 as 

 shown by the identical structure of its principal fracture. 



The weights of the specimens are as follows : 



No. 500.3, 1 1.03 kilograms. 



In PI. XVII, which is a side view of No. 500.14, the distinction 

 between the parts covered with the ramentaceous cortex on the right 

 and those from which this has peeled off on the left, with the exposed 

 edge of this layer, are clearly brought out. 



CYCADELLA KNOWLTONIANA n. sp. 



Pis. XVIII, XIX and XX. 



Trunks of medium size (25cm in diameter), cylindrical, bearing a 

 few small secondary axes ; rock soft, light colored without, dark and 

 variegated within ; organs of the armor horizontal ; leaf scars sub- 

 rhombic, 8-1 2mm wide, 4-6mm high; leaf bases relatively dark, 

 punctate with minute, white-walled tubes ; walls thick, sometimes 

 5mm, soft, white on their outer edges, brown within as shown on the 

 fractures, contrasting strongly with the nearly black leaf bases, the 

 ramentaceous hairs very distinct, showing their mode of origin in the 

 petioles and their passage from the armor into the outer coating which 

 they form, to a thickness in places of nearly 2cm ; reproductive organs 

 few but distinct, usually raised, 16 x25mm in diameter, surrounded 

 by two or more rows of narrow involucral bract scars, the bracts dis- 

 tinctly traceable in longitudinal section to their origin in the receptacle 

 from which also proceed the essential organs in an advanced stage of 

 decay and mineralization ; armor 3-4cm thick, joined to the axis by 

 a very irregular but somewhat definite line, the petioles emerging from 

 different depths as projections of the wood substance ; wood 2-3cm 

 thick, very imperfectly differentiated into two zones, the inner wall, 



