XXXV] TRIPTEROSPERMUM, ETC. 321 



in T. Parkinsoni ; but for a comparison of these with other types 

 of fossil and recent seeds the reader is referred to Salisbury's 

 summary 1 . 



Tripterospermum. Brongniart. 



The seed on which this genus was founded by Brongniart 2 

 is clearly very closely related to Trigonocarpus and, as Oliver 3 

 says, the distinguishing character described by the author of the 

 genus is unimportant. Brongniart describes the type species, 

 T. rostratum, as characterised by the presence of three prominent 

 wings composed of a testa differentiated into an inner hard tissue 

 and an outer lacunar tissue. It is, however, hardly possible to 

 say whether the outer soft tissue was originally flattened in the 

 form of ' wings ' or pressed down on to the harder shell. Renault 4 

 notes the association of seeds that he refers to this genus with 

 the leaves of Dorycordaites , but apart from the improbability of 

 any connexion between Tripterospermum and Cordaites, Renault's- 

 seeds are too imperfect to demonstrate their identity with Brong- 

 niart's genus. Kidston 5 has described an impression of a three- 

 winged seed from the coal-field of Staffordshire as Tripterospermum 

 ellipticum, a form described on page 357 as Polypterocarpus anglicus 

 (fig. 496, B). 



Ptyehotesta. Brongniart. 



The type-species of this genus 6 , Ptyehotesta tennis 7 , about 3 cm. 

 long, is characterised by six very prominent flanges or wings 

 formed by the fissured or folded sclerotesta (fig. 495, B). There 

 is no information as to the vascular supply or other anatomical 

 details. It is not at all improbable that there is no real 

 distinction between this genus and Brongniart's genus Hexaptero- 

 spermum. 



Hexapterospernmm. Brongniart. 



In this genus Brongniart 8 included two species, Hexaptero- 

 spermum stenopterum and H. pachypterum : the shell is hexagonal 



Salisbury (14). 2 Brongniart (74) p. 252, PL xxn. figs. 68. 



Oliver (04) B. p. 391. 4 Renault (96) A. p. 404. 



Kidston (14) p. 157. TTTI^, a plate or fold. 



Brongniart (74) p. 253, PL xxn. figs. 911; (81) p. 26. 

 Ibid. p. 254, PL xxn. figs. 1214; (81) p. 26. 



s. m 21 



