30 IHINNFELDIA. 



indeed tie impossibility, of distinguisMng between specimens 

 figured by different authors as species of Thinnfeldia, Lomatopteris, 

 and Cyeadopteris, becomes apparent on a careful comparison of 

 the published drawings. I am disposed to take the view that 

 the better plan is to employ Ettingshausen's generic name 

 Thinnfeldia in a fairly comprehensive sense, including in it 

 2igno's Cycadopteris and Sohimper's Lomatopteris. Such evidence 

 as we possess points to a close relationship between the plants 

 referred to these three genera, and I believe justifies their 

 inclusion under one name. Until we know something of the 

 reproductive organs we cannot expect to arrive at a satisfactory 

 conclusion as to the precise affinity of these various fossils, and 

 we are unable, in the present state of our knowledge, to point to 

 satisfactory distinguishing features of sufficient importance to 

 serve as generic criteria. 



This is not the place to attempt a critical examination of the 

 numerous Mesozoic fossils described as species of Thinnfeldia, and 

 imtil we know more about the reproductive organs of the plants 

 which conform more or less closely to Ettingshausen's genus, there 

 is little to be gained by discussing specific distinctions. Attention 

 should, however, be called to a paper published in the Bulletin of 

 the Torrey Botanical Club (August, 1903) entitled The American 

 Species referred to Thinnfeldia} The author deals with forms 

 recorded by Fontaine, Hollick, Knowlton, Lesquereux, and 

 Newberry. He comes to the conclusion that many of the species 

 included by American writers under Thinnfeldia differ generically 

 from European forms obtained from lower geological horizons. 

 The Middle and Upper Cretaceous species he designates by a new 

 name, Protophyllocladus. It is undoubtedly true that the term 

 Thinnfeldia has been used in too wide a sense, including plant- 

 fragments which afford no evidence of close relationship. Mr. Berry 

 draws attention to the fact that the later Mesozoic forms from 

 American rocks referred to Thinnfeldia do not closely conform 

 to the typical species recorded from Jurassic and Ehsetic strata. 

 He states that a careful comparison of the fossils from Cretaceous 

 rocks with the living material available at the New York Botanical 

 Garden, has "thoroughly convinced " him that " all the Middle and 



1 Berry (03). 



