XXXV] DECAGONOCARPTJS 357 



as Hexapterospermum Noeggerathi (fig. 506, H), and another 

 British example is afforded by Hexagonocarpus Hookeri Kidst. 1 , 

 a rare fossil in the South Staffordshire coalfield. It is impossible 

 confidently to assign these ribbed casts to genera founded on 

 petrified specimens as they almost certainly belong to different 

 types, but the employment of the name Hexagonocarpus may 

 conveniently be used for casts or impressions of seeds with six 

 longitudinal ribs differing in their relatively broader and less 

 prominent form from the wing-like flanges of Polypterocarpus 

 (cf. fig. 496, B). The seeds described by Dr P. Bertrand 2 as 

 Hexapterospermum modestae, and believed by him to belong to 

 a plant with Neuropteris fronds, should be included in Hexagono- 

 carpus as we have no definite knowledge of their anatomical 

 features. 



Deeagonocarpus. Renault. 



This name, proposed by Renault 3 , is applied to seeds without 

 petrified tissues characterised by ten ribs ; an example is afforded 

 by Decagonocarpus olivaeformis from the Commentry coalfield, 

 an elliptical seed which bears a close resemblance to Holcospermum 

 sulcatum (fig. 506, A) except in the smaller number of ribs. 



Polypterocarpus. Grand' Eury. 



Grand' Eury 4 adopted this generic name for seeds from St 

 Etienne characterised by the presence of three, six, or more deep 

 wings or flanges. The term Pterospermum has recently been pro- 

 posed by Arber 5 for a seed from the Coal Measures of Staffordshire, 

 which he names P. anglicum: the type-species of the genus has 

 three deep wings, one from each angle. For the same seed 

 Kidston 6 proposed the name Tripterospermum ellipticum, but as 

 Arber's account was published first his specific name has priority. 

 Pterospermum had, however, been previously used for a genus 

 of Sterculiaceae, and partly on this account but mainly because 

 Grand' Eury 's genus Polypterocarpus is available the latter designa- 

 tion is adopted. In Polypterocarpus anglicus (fig. 496, B) the 



1 Kidston (14) p. 165. 2 Bertrand, P. (13) PI. VIL 



3 Renault and Zeiller (88) A. p. 651, PL LXXII. fig. 56 

 * Grand'Eury (77) A. p. 185, Pis. xv., xvi, 



5 Arber (14) pp. 93, 104, PI. vin. figs. 51, 52. 



6 Kidston (14) p. 157, PL xiv. figs. 1, 2. 



