THE JURASSIC FLORA OF SUTHERLAND. 675 



Filicineae or Pteridospermse (?). 



Thinnfeldia, Ettingshausen. 



The determination of the numerous fragmentary specimens dealt with under this 

 genus is a difficult task in view of the lack of large examples, which would enable one 

 to determine the range of variation as regards the shape and size of the ultimate 

 segments on a single frond. The more complete specimens figured by Fbistmantel 

 from Australia * show that Thinnfeldia leaves reached a considerable size and 

 demonstrate the small value of the size of the pinnules as a specific criterion. 

 Thinnfeldia is a genus of which our knowledge is very incomplete, and no little confusion 

 has been caused by the use of such generic names as Lomatopteris, Cycadopteris, 

 and other designations for fronds which exhibit a close agreement in habit and texture. 



Thinnfeldia rhomboidalis, Ett. (PI. IV. figs. 66, 70, 70A, 72 ; PI. V. 

 figs. 82, 83, 83A; PI. VII. photo. 21.) 



1852. Thinnfeldia rhomboidalis, Ettingshausen, Abh. k.k. yeol. Reichs., Bd. i., Abt. 3, p. 2, pi. i. 



figs. 4-7. 



1853. Pachypteris Thinnfeldi, Andrae, ibid., Bd. ii., Abt. 4, p. 43, pi. xi. fig. 6; pi. xii. figs. 7, 9. 



The imperfectly preserved specimen represented in fig. 66, PI. IV., which appears 

 to be identical with some of the Lias specimens on which Ettingshausen founded the 

 species, illustrates a considerable difference in the size of the pinnules on a single axis. 

 The pinnules of this type are characterised by the decurrent lower margin and by the 

 narrow and usually fairly deep sinus between the upper portion of the base of the 

 lamina and the axis of the pinna or rachis. The venation is very indistinct, but a 

 midrib caD be seen in some of the segments giving off acute secondary veins. 



The small piece of a pinna shown in fig. 70 bears pinnules of the form of the upper 

 segments seen in fig. 66. Fig. 70 A shows a slightly narrower and longer pinnule with 

 a distinct midrib and the same sudden curve of the upper edge of the lamina. This is 

 precisely like a fragment figured by Moller from the Lower Jurassic of Bornholm 

 as T. rhomboidalis .f The large specimen represented in fig. 83, PI. V., has a strong 

 axis bearing several incomplete pinnules which differ in their greater length and more 

 linear form from those shown in fig. 66, PI. IV. : this difference is probably well within 

 the range of variation met with in the fronds of the same plant. The venation is 

 much more clearly preserved in the fragment (slightly enlarged) in fig. 83 A. With 

 this species I associate a specimen with smaller pinnules, a portion of which is represented 

 in fig. 82, PI. V. ; the habit is bi-pinnate, the ultimate segments agree in shape and 

 manner of attachment with those seen in figs. 66, 70, 70 A, PL IV. This example 

 agrees closely with a small Rhaetic form figured by Schenk J as T. rhomboidalis, and 



* Feistmantel (90), pis. xxiv., xxv. t Moller (02), pi. ii fig. 18. \ Schenk (67), pi. xxvii. fig. 6. 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART IV. (NO. 23). 100 



