MARYLAND GEOLOGICAL SUHVEY 827 



base. Petiole and midrib very stout. Lateral primaries stout but some- 

 what less so than the midrib, opposite, curved, diverging from the midrib 

 at an angle of about 45, or more rather than less, inserted some distance 

 (about 1 cm.) above the peltate base. Secondaries numerous, rather 

 strong, approximately parallel, diverging from the primaries at angles of 

 about 45 or more, camptodrome. Tertiaries well marked, transverse, of 

 a style common to Ficus, Platanus, Sassafras, etc. Margin entire, some- 

 what undulate or sublobate in some specimens. Texture coriaceous. The 

 basal peltate shield varies from broadly rounded to suborbicular and in 

 some specimens it is sublobate with a craspedodrome downwardly directed 

 secondary running to the tip of each lobule. Where it is simply rounded 

 the secondaries are all camptodrome. 



This species was described by Professor Lesquereux in 1874 and was 

 based upon material from the Dakota sandstone of Kansas, to which 

 horizon the genus has been hitherto confined. This species is, however, 

 not uncommon in the Raritan deposits of Maryland where it is associated 

 with representatives of the genus Protophyllum , another peculiar Dakota 

 sandstone series of forms. The material is unfortunately rather poorly 

 preserved, having been much macerated before fossilization, but it is com- 

 plete enough, as is shown by the specimens figured, for certainly in 

 identification. 



The genus Aspidiopliyllum, in which three species have been described 

 has never had its botanical affinity satisfactorily determined, although 

 it is probably related to Protophyllum. Professor Lesquereux fancied 

 that it was related to his Dakota species of Sassafras (Araliopsis), 

 and he also pointed out its resemblance to some of the European forms 

 referred to Zenker's genus Credneria. Professor Ward was disposed to 

 regard it as related to Platanus, and certainly the species Aspidiopliyllum 

 dentatum Lesquereux is very close to those species of Platanus, which, like 

 Platanus basilolata Ward or Platanus appendiculata Lesquereux, have a 

 peltate basilar shield, a condition exhibited as an atavistic character in 

 occasional leaves of the modern Platanus occidentalis Linne. Schenk 

 was disposed to consider Aspidiopliyllum as a member of the family 



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