320 TEIGONOCAEPAIiBS [CH. 



true Trigonocarpus, there is also evidence of splitting. Arber 

 points out that the species Rhabdocarpus Boschianus Berg, is 

 founded on a Trigonocarpus from which the outer flesh has 

 disappeared leaving the shell as the external covering. Trigono- 

 carpus seeds are widely distributed in Carboniferous and Permian 

 rocks in Europe and North America: from the latter continent 

 Newberry^ has described several different forms that afford 

 good examples of the abundance and variety of the genus. Some 

 of the specimens included by Newberry^ in Trigonocarpus are 

 probably distinct generic types: his species T. multicarinatus 

 may be identical with the ribbed cast shown in fig. 506, A. 

 The casts described by Lindley and Hutton and by other authors 

 as T. Dawesi^ are nearly 5 cm. long, and if these are correctly 

 included in the genus they point to the occurrence of seeds much 

 larger than the type-species. The French species Trigonocarpus 

 pusillus* Brongn., one of the smallest Palaeozoic seeds, from 

 6-5 to 15 mm. long, differs from Trigonocarpus Parkinsoni and 

 T. shorensis in the absence of prominent ribs and in the much 

 feebler development of the sarcotesta. Specimens of the German 

 type T. sporites Weiss, believed by some authors to be megaspores, 

 were described by Zeiller^ from Valenciennes as seeds: these 

 are from 2-5 to 3-5 mm. long and have three small ribs. Zeiller 

 quotes the presence of cell-outhnes on the surface as evidence of 

 their seed-nature, but it may be that this feature represents a 

 sculpturing of the exine of a spore. Typical Trigonocarpus 

 seeds agree in several morphological characters with those of 

 recent Cycads. They differ in the lack of a lateral union between 

 nucellus and integument; the presence of nuceUar tracheids, 

 though a feature shared with Bowenia, distinguishes them from 

 the majority of recent Cycadean seeds. In the comparatively 

 long and fleshy micropylar tube a seed of Encephalartos Lehmanni 

 presents a fairly close resemblance to a Trigonocarpus. Salisbury 

 has pointed out that the three species T. Parkinsoni, T. shorensis, 

 T. pusillus form a consecutive series illustrating the gradual 

 disappearance of the secondary ribs that form a prominent feature 



1 Newberry (73). 2 ji,id. PI. xiji. fig. 8. 



= Page 123. * Oliver (04^) B. See also Renault (96) A. p. 398. 



« Zeiller (88) A. p. 652, PL 94, fig. 17. 



