118 



MEDULLOSEAE 



[CH. 



who adopted this form,, states that Brongniart substituted Trigono- 

 carpon for Trigonocarpum in his Tableau 1 , but in that work the 

 original termination is used, the form Trigonocarpon, probably 

 the result of a slip, appearing only in the index. In his later 

 work on seeds Brongniart adopted the name Trigonocarpus, and 

 in recent years this has been widely employed. Among other 

 species named by Brongniart are two previously referred by 

 Sternberg to Palmacites. Several examples of Brongniart's genus 

 were described by Lindley and Hutton, and in their descrip- 

 tion of T. Noeggerathii the statement is made that a fractured 

 specimen demonstrated that 'the fossil in its ordinary state is 



FIG. 423. Casts of the seed-cavity of Trigonocarpus Parkinsoni. 

 (Manchester Museum. \ nat. size.) 



an interior part divested of fleshy covering' 2 ; this suspicion of 

 the true nature of the nut-like fossils was afterwards proved 

 correct by the investigations of Hooker and Binney 3 and by the 

 later work of Williamson. The specimens on which the genus 

 was founded are casts of seed-cavities and it is in this state that 

 the seeds are usually preserved, often in large numbers, in the 

 sandstones of the Coal Measures, as in the block shown in fig. 423 

 from the famous quarry at Peel near Bolton, Lancashire. Another 

 type of preservation is represented by the seeds figured by Lindley 

 and Hutton as Carpolithes alata*, but the generic identity of the 

 two states was not recognised until the discovery of petrified 

 material afforded the clue. Figs. 424, 1, 425 illustrate the appear- 

 ance of Trigonocarpus when preserved as a carbonised impression 



1 Brongniart (49) A. p. 91. 2 Lindley and Hutton (35) A. p. 172. 



3 Hooker and Binney (55). 4 Lindley and Hutton (33) A. PL 87. 



