46 THE PALEONTOLOGIC RECORD 



malian skeleton has brought about many morphological modifications 

 from those shown in the Batrachia and Eeptilia. We find the skull 

 loses the prefrontal and postfrontal bones, the mandible is simplified, 

 the limb bones show a development of terminal epiphyses with ossifica- 

 tion to the center of the vertebras and the bones of the pelvic arch are 

 ossified. From the beginning of the Tertiary time a marvelous variety 

 of morphological characters appears, and without the fossil types we 

 should have but an inadequate conception of this great phylum. 



The contributions of paleobotany to morphology are in some re- 

 spects quite as striking as those of paleozoology. 



The fossil Thallophytes have not furnished any very striking varia- 

 tions from their present morphological features, while the Bryophytes 

 are scarcely represented as fossils except in very recent deposits. 



The remaining phyla, the Pteridospermatophytes, the Pteridophytes 

 and the Spermatophytes have their oldest known beginnings as far 

 back as the Devonian and their study has enormously widened the 

 bounds of plant morphology. 



The Pteridospermatophytes, which are confined to the Paleozoic, 

 are in habit and vegetative morphology ferns in methods of repro- 

 duction and in the morphology of their reproductive organs typical seed 

 plants. They alter our whole conception of ferns and seed plants and 

 in their significance are comparable to archetypal vertebrata, the acqui- 

 sition of the seed habit in plants and the vertebral column in animals 

 probably marking the culmination of the transfer of vital activity from 

 aquatic to terrestrial conditions. 



In the Pteridophytes the extinct Paleozoic class, the Sphenophyllales, 

 is significant, since the morphology of the distinct lycopod and Equi- 

 setum lines seems to merge in this group. The lycopod type, itself 

 represented in the existing flora by six or seven genera of herbaceous 

 plants, monotonously uniform in their morphology, is found in the 

 Paleozoic to constitute one of the chief units in the arborescent flora 

 with numerous species of complex organization, whose stem, foliar and 

 reproductive morphology was quite unknown to botanists (Lepido- 

 dendron, Sigillaria, etc.). The Equisetum type furnishes a like 

 case. With few existing species of minor importance and uniform 

 morphology we find in the Paleozoic a host of forms, many of them 

 arborescent and of varied and complex structure (Catamites, Archceo- 

 calamites, etc.). Similar examples could be drawn from the fossil 

 representatives of the true ferns. 



In the Spermatophytes another wholly extinct class, the Cordaitales, 

 embraces a curiously organized group of conifers extending back to the 

 oldest horizons from which land plants are found, and continuing to 

 the close of the Paleozoic as one of the most abundant as well as the 

 highest type of pre-Mesozoic r>lant. In the older Mesozoic we find t\TO 



