342 CARDIOCABPALES [CH. 



the presence of fibrous strands and are not ribs in the ordinary 

 sense. The outer tissue shows numerous longitudinal striations 

 due presumably to the presence of fibrous elements in the sarco- 

 testa like those shown in the petrified seed represented in fig. 

 501,0. The genus is defined by Berger as follows: 'Semina 

 ovata vel elUptico-oblonga secundum longitudinem parallele 

 nervosa vel tenuissime striata, putamine (interdum deficiente) 

 instructa.' As used by Berger and many other authors Rhabdor 

 carpus includes a miscellaneous collection of seeds often differing 

 widely from the type-species. Many of the examples correctly 

 referred to Berger's genus are platyspermic though a bilateral 

 symmetry is by no means always clear. Eenault and Zeiller^ 

 in their definition of Rhabdocarpus include bilateral symmetry 

 as a characteristic feature and speak of the seeds as oblong or 

 oval with a pointed or truncate apex and a rounded base. Im- 

 pressions of Rhabdocarpus differ from those of Cardiocarpus or 

 Cordaicarpus in their more elongate form, always longer than 

 broad, and in the absence of a basal sinus. The seeds found 

 attached to Neuropteris pinnae and, in external features, agreeing 

 with many specimens included in Berger's genus, have been 

 transferred by P. Bertrand^ and Arber^ to a new genus Neuro- 

 spermum* Arber* in his recent revision of British seeds proposes 

 to restrict the name Rhabdocarpus to platyspermic seeds having 

 a 'large unsymmetrical nucule enclosed in a large unsymmetrical 

 wing or sarcotesta,' that is to forms symmetrical in one plane. 

 In this category he includes Rhabdocarpus tunicatus Berg. (fig. 506> 

 K) and R. subtunicatus^ Grand'Eury, but it is not clear on what 

 grounds Berger's species is spoken of as symmetrical in only one 

 plane: in the species R. Lilleanus AxbP the symmetry is hardly 

 sufficiently well defined to rank as a generic character. In thei 

 case of the Neuropteris seeds the apical snout is shghtly curved, 

 thus giving them an unsymmetrical appearance (cf. fig. 422, p. 114). 

 The Carboniferous and Permian seeds usually referred to Rhabdo- 



> Benault and ZeiUer (88) A. p. 635. ' Bertrand, P. (13). 



» Arber (14) p. 103. 



« See page 116. « Arber (14) p. 87. 



« Zeiller (92^) A. PI. xv. fig. 11. 



' Arber (14) PI. vn. fig. 21. 



