FEIJNS— PECOPTERIDE.E— PECOPTEEIS. 87 



appeared that Ibniis belonging to more than one species had been inchided 

 under each name. Afterwards, when additional collections had come, and 

 the series of allied forms was represented by nearly a thousand specimens, 

 it was evident that a revision would be necessary. Pending, however, the 

 removal of the Lacoe collection to Washington, all further study of this 

 group in the material from Missouri was postponed. Since that time the 

 cousunnnation of the gift of Mr. Lacoe's invaluable collection of Paleozoic 

 plants to the United States National Museum has given me the opportunity 

 to study the magnificent series of Pecoterids therein, including the types 

 of species contained in the Missouri material. Accordingly, in the following- 

 discussions of the species concerned, I shall make reference to the specimens 

 identified by Professor Lesquereux, some of which are herein illustrated. 



Among the collections there are several hundred specimens represent- 

 ing a well-defined species, which is distinguished from the other forms 

 present by the close oblong pinna?., with smooth rachises and very slightly 

 rugose, opaque, nearly smooth lamina in which the nerves are generally 

 fairly well shown. The Tertiary pinnae are oblong-linear or oblong,, slightly 

 contracted at the base, the sides nearly parallel, and somewhat abruptly 

 contracted at the top in an acute point terminated by an ovate pimiule 



The pinnules are close, open nearly at a right angle to the rachis, 

 proportionateh" narrow, hardly decurrent, and very uneven in their position. 

 The lamina is depi'essed rather strongly over the midiib and repand at the 

 margin. The nerves differ from those of the other species l^y their more 

 erect position near the midrib and the more strongly arched nervils, which 

 pass more nearly at right angles to the margin, besides being irregular or 

 somewhat crooked and closer. 



A large slab containing segments of parallel primary pinn^ of this 

 plant, the broad section of whose rachises indicates a very great size for 

 the species, is shown in PI. XXIX. These segments are interesting from 

 the fact that the parallelism of their position seems to indicate a relation- 

 ship of both the contained segments as subdivisions of a pinna of a still 

 higher order, a condition still more strongly suggested by a section of a 

 fertile frond on another slab. In this fertile specimen a section of a pinnate 

 rachis of nearly the size seen in the larger slab is seen in union at an oblique 

 angle with a still larger rachis, the entire width of which is unfortunately 

 not shown in the specimen. 



