XXVIl] 



THINNFELDIA 



539 



The portion of a lobed pinnule shown in fig. 356, B, 

 illustrates a form of segment intermediate between the linear 

 type with a midrib and a row of shorter pinnules without 

 a median vein. Fig. 356, D, represents another instance of 

 variation in the arrangement of the veins in segments of 

 different sizes. Various specific and generic names have been 

 assigned to Thinnfeldia fronds of Rhaetic age on the ground of 

 the occurrence of pinnules longer and narrower than those 



Fia. 356. A— D. Thinnfeldia odontopteroides {iiorvia) 

 E. Ptilozamites. (E, after Nathorst.) 



usually associated with T. odontopteroides ; but in view of the 

 range of variation met with in a single leaf it is advisable to 

 extend rather than to restrict the boundary of what we are 

 pleased to regard as a specific type. 



The name Thinnfeldia lancifolia has been applied by 

 Morris to fossils from Australia which may be identified with 

 T. odontopteroides, and the same designation is employed by 



