30 THE OLDEE MESOZOIC FLOEA OP VIEGINIA. 



slightly rounded at base, and more or less acute at their extremities, being separate 

 to the rachis of the pinnae, and inserted by their entire base, either subopposite or 

 alternate, the lowest pinnule on the lower side of the pinna being often inserted half 

 upon the principal rachis of the frond. Pinnules of the fertile frond rounded or 

 semicircular in form, thick, coriaceous, somewhat convex, and granulated by the 

 fructification. Pinnules of both sterile and fertile fronds more and more united 

 towards the extremity of the pinnae and towards the upper part of the frond, while 

 at the same time the pinna? become shortened, until finally, towards the summit, the 

 pinnae are reduced to pinnules. Middle nerve of the fertile pinnules, none. Nerves 

 composing about three groups, which spring from a point below the center of the 

 pinnule and branching dichotomously and flabellately, fill the pinnule. Middle nerve 

 of the sterile pinnules rather strong at its insertion, sending off branches from its 

 base and at intervals higher up, the latter quite obliquely, and finally towards its 

 summit being dissolved into branches. Lateral nerves lower down branching more 

 frequently than those towards the extremity of the pinnules, all slender, but very 

 sharply defined and distinct. Fructification in the form of rounded sporangia placed 

 between the nerves and covering the under surface of the pinnules. 



The large number of well-preserved specimens that I obtained of this 

 fine species enables me to give a very complete account of nearly all parts 

 of the plant. It seems to have been an arborescent species, and the large 

 fragments depicted in the figures appear to be primary pinnae which were 

 once attached in a pinnate manner to some large rachis, as in the case of A. 

 UnncBcefolius, causing the plant to be probably at least tripinnate. Plate XI, 

 Fig. 1, Plate XII, Fig. 1, seem to represent the middle portions of the pri- 

 mary pinnae, or it may be of the fronds. The channeled rachis is well 

 marked in this species. The lower portion of the plant seems to have borne 

 smaller pinna? and pinnules, for Plate XI, Fig. 2, evidently represents a 

 portion of the pinna or frond lower down than the parts given in the above- 

 named figures. Perhaps this feature is analogous to the perceptible dimi- 

 nution in the size of the pinnules often seen in this plant toward the inser- 

 tion of the pinna? of the last order, which is an unusual feature. The 

 pinnae of the last order, or ultimate pinnae, were very long and slender, so 

 that their tips are almost never preserved. I have succeeded in finding 

 only one distinctly shown. This is represented by Plate VIII, Fig. 2. Here 

 the pinnules are seen to become more and more united, and the termina- 

 tions of the pinna? of the middle and lower parts of the plant perhaps thus 

 possess the character of the entire pinna? from the upper part of this fossil, 

 where all the pinnules of the pinna? are . becoming united, as is shown in 



