G6 PP. REPOKT OF PROGEESS. FONTAINE & WHITE. 



bers of tlie stipes are found, many 5 or 6 inches in diam- 

 eter. 



At other localities we find the variety polymorpha, given 

 by Brongniart as a distinct species (P. polymorpha.) This 

 form usually occurs at different localities from those where 

 the forms of Miltoni are abundant, and the facies of the 

 plant is different, the pinnules being broader, longer, and 

 less rounded at the extremity. Some splendid specimens 

 of i)rimary pinnae, complete to the extremity, are found 

 more than a foot long. Our forms of Miltoni agree pre- 

 cisely with those given by Artis, and have a somewhat differ- 

 ent facies from that of Brongniart' s plant. 



Pecopteris dentata, Brongt. PL XXII, Figs. 1-5. 



We find at Cassville, in the roof shales of the Waynes- 

 burg Coal, several forms of a plant which is so closely allied 

 to this very polymorphous s^iecies that we do not think it 

 proper to separate them further than as varieties. Figs. 

 1-4, PI. XXII, show a well marked type, which is the most 

 abundant form, and might be denominated P. deniata, var. 

 crenata. The form figured in Fig. 4 exhibits some points 

 of difference from that given in Fig. 1, in the pinnules being- 

 narrower and more constricted at the base, and more remote, 

 and also in the tendency to become shorter towards the in- 

 sertion of the ultimate pinnae. The form given in Fig. 1 

 assumes more of the aspect of the typical plumosa form of 

 P. dentata, especially in the lower pinnae. Seen sejiarately, 

 the two plants might be taken as distinct species, or at least 

 varieties, but we have so many intermediate forms at this 

 place that no dividing line can be drawn between them. 



The plant figured on plate XXII, in Fig. 2, differs a good 

 deal from all the forms of the var. crenata above mentioned, 

 and assumes the facies of the plumosa form of dentata. It 

 differs how^ever from Brongniart' s plumosa in its more mi- 

 nutely dentate pinnules in the small size and delicacy of 

 the pinnules, which, unlike the European plumosa, show 

 no tendency to increase in size as we descend to lower pin- 

 nae. It is still more widely separated from the form identi- 



