CHAPTER II 



BENNETTITALES 



Bennettitales are as characteristic of the mesozoic flora, from the 

 Trias to the Lower Cretaceous, as are the Cycadofilicales of the paleo- 

 zoic. The historical and morphological succession is so distinct that 

 there seems to be no reasonable doubt of the phylogenetic connection 

 of the two groups. The Mesozoic has long been called " the age of 

 cycads," but it was recognized that the mesozoic forms differ so much 

 from the modern ones as to justify speaking of them as "anomalous" 

 or "aberrant" cycads. The type genus, Bennettites, was described 

 by Carruthers (2) in 1867, and in 1870 he established (4) the group 

 Bennettiteae as an assemblage of aberrant Cycadales. 



The best knowii foreign localities for the remains of Bennettitales 

 are in Western Europe and India; but by far the richest display of 

 these forms has been found in the United States and Mexico. These 

 North American forms have been described chiefly by Wasd (ii, 12), 

 and their structure has been skilfully investigated and set forth in 

 great detail by Wieland (22) . The three prominent American locali- 

 ties that have yielded material are in Maryland, in the Black Hills 

 of South Dakota and Wyoming, and in the Freezeout Hills of Wyo- 

 ming; while the recently discovered Mexican locahty is in the moun- 

 tains of western Oaxaca (30). The remarkable Mexican deposits 

 were discovered by Wieland (30) in 1909, and they bid fair to surpass 

 in abundance of remains and in interest even those of the United States. 

 The region is a great plateau of Oaxaca on the southern edge of the 

 Cordilleras facing the Pacific, and known locally as "Mixteca Alta." 

 A section through 2,000 feet of "Rhat-Liassic" is full of the remains 

 of cycadophytes, and among them there is a profusion of the strobili 

 of Williamsonia, a most interesting addition to the cycadophyte flora 

 of America. Unfortunately, silicified remains have not yet been 

 found. 



The best known and largest genera of the group are Bennettites, 

 Cycadeoidea, and Cycadella; other genera (not American) are Buck- 

 landia, Williamsonia (also Mexican), Cycadocephalus, Yatesia, 



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