290 D. WHITE — AGE OF LOWER COALS OF HENRY CO., MISSOURI. 



TiENIOPHYLLE^E : GYMNOSPERMS '. 



Tzeniophyllum, 1. Cardiocarpon, 1. 



Lepidoxylon, 1. Rhabdocarpos, 2. 



Gymnosperms : Titanophyllum (?), 1. 



Cordaites, 2. Dkranophyllum, 1. 



Cordaianihus, 2. Animalia (?) : 

 Cordaicarpon, 1. - Palxoxyris, 1. 



From the above epitome it will be noted that most of the commoner 

 Mesocarboniferous plant genera of the world are present in the lower 

 coals of Henry county. The ferns are especially preponderant, while 

 the Sigillariese are comparatively poorly represented. The relatively 

 large number of species of Pecopteris is notable, although two or three of 

 the latter, including those which are generally regarded as indicating a 

 higher zone than that in which some of the forms of Pseudopecopteris and 

 Mariopteris are common, are extremely rare. 



Distribution of the Species in other American Basins. 



Of the plants included in the foregoing summary, a portion* are new 

 or have not been found in other regions, and therefore offer only inferen- 

 tial and subordinate correlative aid, such as may be cautiously drawn 

 from their biological relations or the distribution of the species to which 

 they appear to be most closely related. 



Another category of species of little definite help in chronologic studies 

 includes those having a wide vertical range. Examples of such are Pecop- 

 teris dentata. Brongn. ; Neuropteris scheuchzeri, Hoffm.,; Neuropteris rari- 

 nervis, Bunb. ; species of Calamities ; Aster ophyllites equisetiformis, (Schloth.) 

 Brongn. ; Annidaria stellala, (Schloth.) Wood ; Annularia sphenophylloides, 

 (Zenk.) Gutb. ; Sphenophylhcm emarginatum, Brongn. ; Sigillaria tessellata, 

 (Steinh.) Brongn., and Rhabdocarpos multistriatus, (Presl) Lx., although 

 several of these species are found on examination to be clearly differen- 

 tiated in forms or varieties of limited vertical range and consequent 

 unquestionable stratigraphic value.f It should, however, at the outset 

 be stated that of the entire flora I have not seen more than three or four 

 forms common to the Pottsville series, and that only one, of doubtful 

 identity, among these occurs below the upper (Sewanee) division of that 

 series. On the other hand, many of the species of wide vertical range 

 are in a general way somewhat characteristic of the Alleghany series. 



* About 30 species. 



fThe occasionally misleading effect of the recorded distribution is especially plain when speci- 

 mens from widely separated groups, as. for example, the Pottsville series (xii) or the Alleghany 

 series (xiii), and from the Dunkard Creek series (xvi), independently identified, perhaps by dif- 

 ferent authors or merely from the literature, under the same name, are brought contiguously into 

 a comparison. 



