22 FLORA OF LOWER COAL MEASURES OF MISSOURI. 



Sphenopterids ; or he might have restricted the genus Pseuclopecopteris to the 

 species which woukl remain in it at present after taking out those covered 

 by the characters of Mariopteris. Thus it appears that the chief difference — 

 a rather important one — in the original scope of the two genera was the 

 inckision of the round pinnuled or Neuropteroid Sphenopterids in Lesque- 

 reux's genus. The inckision in- Pseudopecopteris of certain Pecopteroid 

 species, on account of a supposed method of di^dsion in their fronds, is a 

 subordinate feature and need not be considered at present. 



In my report on the plants from the Carboniferous outliers,' I have 

 refeiTed Pseuclopecopteris mazoniana Lx. to the genus Mariopteris on account 

 of its apparent affinities with the muricata group. Although after an 

 examination of the figured specimens from Mazon Creek, Illinois, I 

 am inclined to believe that not all the examples identified by Lesquereux 

 as Pseudo])ecopteris mazoniana belong in reality to the same species, it 

 still seems to me probable that some of the types of that species, which 

 was given first place in the genus Pseudopecopteris by its author, belong 

 properly to the muricata group. This group, as Zeiller remarks, is very 

 homogeneous, being composed of quadi-ipartite fronds of the Biplothmemce 

 with Pecopteroid j^innules, the well-developed lamina being entire or 

 slightly lobed or denticulate. Naturally in a classification depending largely 

 on the mode of the basal division of the fronds it is often impossible to 

 determine definitely as to this character; and the gTOuping in such cases is 

 dependent on the features and analogy of the other parts. Thus there 

 seems little doubt of the unity of Ps. nervosa (Brongn.) Lx., Ps. muricata 

 (Schloth.) Lx., Ps. latifolia (L. & H.) Lx., Odontopteris splienopteroides Lx., and 

 Ps. acuta (Brongn.) Lx. within the same group ; and in most of these species 

 the quadripartite character of the frond has been observed, showing their 

 identity with the genus Mariopteris Zeill. I have seen the same mode of 

 division in Ps. Newberryi Lx., and it seems probable that it will also be 

 found to exist in Ps. cordato-ovata (Weiss) Lx. and Ps. SiUimanni (Brongn.) 

 Lx., while several of the forms still included by Zeiller in the genus 

 Dlplothmema bear signs of a generic relation to Mariopteris muricata 

 (Schloth.) Zeill. 



In my former remai'ks on the subject I was disposed to consider the 

 greater portion of the species in Pseudopecopteris as having the essential 



' Bull. U. S. Geol. Surv., No. 98, 1893, p. 46. 



