ends with the Jurassic instead of with the Cretaceous, while the terti- 

 ary for fossil plants closes with the Miocene instead of with the Plio- 



Of the many important discoveries made hy Williamson, the most 

 valuable is the demonstration of the existence of exogenous structure 

 in the Carboniferous Pteridophytes. (Science, Vol. II, 1895.) 



The Appalachian Folds.— The faults and folds in Pennsylvania 

 Anthracite beds are most admirably shown by Dr. Benjamin Smith 

 Lyman in a paper illustrated by thirty-three page plates containing 

 177 sections. These sections were prepared by the author from the 

 valuable cross-section sheets of the State Geological Survey, and are 

 accompanied by a key map showing where the sections are made. 

 From a comparison of these cross sections Dr. Lyman draws the fol- 



" Steep northerly dips in the Pennsylvania anthracite region are 

 much less prevalent than was formerly supposed ; nearly half the ba- 

 sins and saddles are about symmetrical ; nearly three-fourths of the 

 subordinate ones are so in the Western Middle field ; less than quarter 

 of the main ones are so in the Southern field. Again, the subordinate 

 folds throughout the region are confined to subordinate groups of beds 

 of inferior firmness, and are not parellel to the main folds, but prob- 

 ably at uniform profile distances from the maiu axes, so as to descend 

 the flanks of a sinking anticlinal. Further, that the faults are most 

 invariably longitudinal or reversed faults, occasioned by the overtrain- 

 ing of subordinate folds, and corresponding in three-fourths of the 

 cases to an overturned southerly dip, with the upthrow to the south ; 

 such broken subordinate folds, whether dipping southerly or northerly, 

 ride in equal number on the northerly dipping and southerly dipping 

 sides of the main folds ; the stratigraphic throw averages only about 

 62 feet, and never exceeds 160 feet ; the displacement averages 72 feet, 

 and never exceeds 240 feet." (Trans. Amer. Institute Mining Engi- 



The Ancestry of the Testudinata.— In the Naturalist for 

 1885, I advanced the hypothesis that the order of the Testudinata 

 arose from the Paleozoic order of the Theromora. In the latter I in- 

 cluded at that time the forms I afterwards distinguished as an order 

 under the name of Cotylosauria. In 1892 (Transac. Amer. Philosoph. 

 Society, p. 24) I specified that the Testudinata must have been de- 

 rived from this latter order. It is now possible to bring positive evi- 

 dence that this view is correct, since the anticipation so expressed is 



