XXX] TRIGONOCARPUS 123 



(Middle Coal Measures), similar to T. Parkinsoni but much 

 broader in proportion to its length: this species is founded on 

 an impression without structure. 



The species Trigonocarpus Dawesi Lind. and Hutt. 1 , from 

 the Middle Coal Measures of Lancashire, was founded on casts 

 differing in their large dimensions from those of T. Parkinsoni: 

 specimens referred to this species were described by Fiedler 2 

 from Saxony in 1857 and Lesquereux 3 figures similar casts from 

 the Upper Carboniferous and Permian rocks of North America. 



Trigonocarpus shorensis Salisbury. 



This species, founded on specimens from the Lower Coal 

 Measures of Shore, Lancashire 4 , may exceed 4 cm. in length and 

 has a breadth of 2-5 cm. In general plan it agrees with T. Parkin- 

 soni but there are certain well-marked differences : the micropyle 

 is much shorter; the thick sarcotesta, attaining a breadth of 

 6 mm. at the base of the micropyle, is characterised by the presence 

 of six peripherally placed vascular bundles (fig. 426, D, v) in 

 contrast to the deeply embedded bundles of T. Parkinsoni. 

 Below the epidermis of the sarcotesta is a hypoderm formed of 

 radially disposed plates of sclerous tissue similar to that of Myelo- 

 xylon and different from the palisade-like hypoderm of the type- 

 species. Within the sarcotesta is a hard shell, the sclerotesta, 

 characterised by three prominent ribs extending from base to 

 apex and three shorter ribs which reach from the chalaza to 

 about a third of the length of the seed. The fact that the sarco- 

 testa and sclerotesta pass gradually into one another is a point 

 in favour of the view that the integument is a single structure. 

 There appears to be good evidence of the restriction of an inner 

 flesh to the micropylar region, whereas this tissue in T. Parkinsoni 

 was probably continuous over the whole inner face of the sclero- 

 testa. The sarcotesta is lacunar in its outer part as in some other 

 types of Palaeozoic seeds, a feature probably connected with 

 floating efficiency. Trigonocarpus shorensis occurs in association 

 with Myeloxylon petioles, and there is a resemblance between 



1 Lindley and Hutton (37) A. PI. 221 ; Arber loc. cit. p. 95, PI. vi. fig. 8. 



2 Fiedler (57) PI. xxvu. fig. 39. 



3 Lesquereux (80) A. PL 85; (84) A. PI. in. 4 Salisbury (14). 



