FROM THE SECONDARY ROCKS OF BRITAIN. Sgg 



refer Brongniart's BucMcmdia, along with his Clathraria, to Sternberg's older ^enus of 



© " v *"' * - 



the same name. The original Clathraria is still retained by some paleontologists as I 

 good genus of palaeozoic vascular cryptogams l . 



Dr. Mantell gave up his first vague notions of the affinities of these fossils after the 

 publication of the report by Stokes and Webb, when he referred them, with these authors. 

 "to the same tribe of fossil plants as the Lepidodendron of Sternberg, ' ' 'a tribe of 

 vegetables of the ancient world which is common in the Carboniferous strata, and appears 

 to have held an intermediate place between the Equiseta and the Palms." 8 In order that 

 his readers might the more clearly realize the aspect of the fossil, he reproduced a figure of 

 Sternberg's Lepidodendron dichotomum, in which the form and attachment of the leaves 

 are shown. Some years later 3 he adopted the opinion of Brongniart, and held that they ap- 

 proximated " very nearly to Dracaena, or rather to Xanthorrhwu." He maintains t his view 

 of their affinities in his numerous publications 4 which so largely contributed to make the 

 new science of Geology popular, until 1847, when "the discovery of more illustrative spe- 

 cimens than those at first obtained indicated their affinity to the C'/cadece, with which 

 M. Brongniart has some years since arranged them" 5 . These specimens, however, were 

 water-worn fragments of a very distinct genus (Bemietti(es), the nature of which I havn 

 been able to determine from the large series of specimens which I have had the oppor- 

 tunity of examining. 



Bucklandia is known only from the impressions of the stems and of the medullary axis 

 of the various species. All the specimens I have seen are casts in the amorphous sub- 

 stance of the rock in which they are imbedded. Mantell says :— " In the strata of the 

 Tilgate Forest the Clathraria are invariably associated with water-worn bones of reptile* 

 pebbles, gravel, and other drift, and are often imbedded in the fluviatile conglomerate 

 which is found in some parts of the Wealden. They appear to have floated down the 

 river with the carcasses and limbs of the reptiles, and at length to have sunk to the bottom, 

 and become imbedded in the mud of the Delta" 6 . The large medulla of the buried stem 

 first yielded to decay ; and into the cavity thus formed the amorphous mud was pn-s^i, 

 moulding itself on the interior of the woody cylinder. Subsequently the whole Of the 

 more indurated tissues perished, and their place was filled with more of the mud which 

 received the impression of the outer surface of the stem with all ite *"*"*» mark- 

 ings. Consequently no information regarding these fossils can be obtained by ^ u " 

 the microscope ; aU must be gathered from the markings impressed on the structured s 



The stems were cylindrical, attaining a height of at least four feet, «*J»^ 

 hiding dichotomously *> one specimen a second d*££ »^*£ £ 

 ducing three equal branches. The stem exhi rts a «£££*« £ do«%mit> 

 sections, and is covered with more or less rhombotdal scars arian e , 



to each other, and in a quincuncial manner. The appendages borne by these 



1 D 



SUK X 



awson, Acadian Geology 



Geolo 



eulogy 01 me South-east ot ungiana ^xcu^, ?. — - lg4 & 



; The Wo»de re of Geolo gy (1838), p. 342 ; The MW* of ^^^ ^ 



Geology of the Isle of Wight (1847), p. 292. 

 VOL. XXVI. 



5 



