29() MESOZOIC FLOKAS OF rMTKl) srATFS. 



Iniiiu'diatcly after leavinj^ the rachis tlie IniiuUe splits up into about three 

 principal hranehes. and those i)ran('h ajjain several times, the entire £;rou]) 

 diversjinfi flahellately so as to fill lli(> pinnule. The iierNation then is much 

 like that of the Aci'ostichites of the Older Mesozoic flora of N'irii'inia. It 

 may he compared with that of .1. )iiicro})hyllus Font., a plant which is a 

 good deal like the one now in question and which was descrihed in Mono- 

 graph United States Geological Survey, \'ol. VI, page 83. 



The nervation of the inferior basal and Haljellate piimules is conformed 

 to the shape of these pinnules. It consij^ts of a nerve btmdle which splits 

 into three main branches, one of which goes into each lobe of the pinnule, 

 giving ofT diverging and forking l)ranches which fill each lol)e. In the less 

 commonly occiu'ring abnoi-mal forms there is some variation from the t^•pe 

 shown in both the l)asal inferior pinnules and in those on the other portions 

 of the ultimate pinnae. The basal inferior pinnules are less deeply lobed 

 than those on the pinnse with normal pinnules, more elliptical in shape, and 

 strongly deflexed along the rachis of the penultimate pinna". They are 

 either elliptical or spatulate in form. 



The other pinnules of these foi-ms are mostly larger than the noi-mal 

 ones. They are ovate to elliptical in shape, obtuse to subacute, rounded 

 ofT at base on both the lower and the upper side, owing to an abrupt nar- 

 rowing of the pimiule innnediately at its attachment to the rachis of the 

 pinna. Some of the forms that are subacute are sometimes ev(Mi acumi- 

 nate f^om the gradual narrowing of the pinnules toward their tips. The 

 nerves in all the pinnules of the abnormal forms are of the same type as 

 those of the coi-responding ones on the normal forms, but the nerves of the 

 more common pinnules are apparently thicker and more vaguely defined 

 than those of the corresponding normal ones. 



PI. LXXI, Fig. 21 , represents a penultimate pinna, carrying portions of 

 several ultimate pinna^, which well show the small pinnules that constitute 

 the normal forms, and also their accompanyitig basal pinnules. Fig. 22 

 gives two of the normal pinnules magnified four di.'iraeters, to show the 

 nervation. Pig. 23 represents ;; portion of a pinna of the abnormal kind, 

 containing the largest ])iiuiulcs found, and Fig. 24 gives a part of a primary 

 pinna of the abnoi-mal kind, which carries j)ortions of three uhimate 

 pinna, showing well the form of the more acute pinnules of this kind, and 

 also j)ortions of their accompanying basal deflexed jiininiles. The nerves 



