CARBONIFEROUS. 167 



caudata, Geinitzand Homer (l.c.), are all, I believe, referable to Lepidodendron 

 Veltheimianum. 



Lepidodendron Jaschei and Lepidodendron gracile, Eb'mer (Palaeontogra- 

 phica, vol. xiii. pi. xxxv. figs. 6, 7), are both young conditions of Lepidodendron 

 Veltheimianum. Similar transverse bars to those occurring on the leaf-scars 

 of Lepidodendron gracile have already been referred to in the case of Lepido- 

 dendron rugosum* 



Bergeria regularis and Bergeria alternans, Schmalhausen (l.c.), appear to be 

 only different conditions of preservation of Lepidodendron Veltheimianum. 



The core of an impression of Lepidodendron Veltheimianum in my own Col- 

 lection agrees so entirely with Knorria acicularis that I have no hesitation in 

 also referring that fossil to this species. The explanation of how this fossil is 

 formed will be learnt from an examination of the internal structure of Lepi- 

 dodendron. As far as the present example of Knorria acicularis is concerned, 

 the more delicate tissue surrounding the central vascular bundle appears to 

 have decayed, and the bundle thus freed has probably floated out of the 

 cortical cylinder, which subsequently became filled with sediment. Pressure 

 then acting on the cortical cylinder has forced the mud which filled its 

 interior up the small channels through which the foliar vascular bundles 

 pass to the leaves ; the bark next appears to have decayed, leaving the 

 impression of its outer surface on the surrounding matrix. The preser- 

 vation of the casts of the vascular bundle channels has been assisted by the 

 decayed bark remaining around them in the form of a fine powder, and so 

 helping to prevent their obliteration by subsequent pressure or infiltration. 

 In this manner are formed the little acicular points (the casts of the channels 

 through which the foliar vascular bundles passed) which characterise Knorria 

 acicularis, Goppert. 



Some specimens of Knorria imbricata appear to be formed by a partial 

 decay of the outer surface of the bark of Lepidodendron before fossilisation 

 takes place. It is impossible to correlate the various named species of 

 Knorria with the plants to which they really belong, as any species of Lepi- 

 dodendron might produce one or more so-called species of Knorria, according 

 to the amount of decay that had taken place in the plant and the conditions 

 that had attended its mineralisation. 



Lepidophloios and the Clathrarian-Sigillaria might also form Knorria-like 

 fossils. 



The type of Flemingites Pedroanus, Carruthers, is in the Collection. I 

 have failed to see any character in which it differs from Lepidodendron 

 Veltheimianum. 



good example of ^Lepidodendron Veltheimianum showing 

 scars. This example was subsequentiy named Ulodendron Allani by Buck- 

 land, and Lepidodendron ornatissimum by Brongniart. Lindley and Hutton 

 mention Allan's figure as synonymous with their Ulodendron minus, but this 

 appears to be a mistake, for Allan's specimen shows the Lepidodendroid 

 leaf-scar, whereas Lindley and Hutton's plant belongs to the Sigillarian 

 section of Ulodendron. 



The plate of Ulodendron minus, L. and H., does not at first lead one to 

 this view, but from an examination of the counterpart of their fossil, all 

 which is now preserved of their type,f I have been led to this conclusion. 

 Ulodendron majus, L. and H., is only an older and larger example of their 

 Ulodendron minus ; hence its supposed identity with Rhodes' pi. iii. fig. 1, is 

 also erroneous. Lepidodendron ornatissimum and Rhodes' pi. iii. figs. 1-8 

 are referable to Lepidodendron Veltheimianum. 



Here must likewise be placed Eichwald's figures of Ulodendron ellipticum, 



* See note under Lepidodendron Sternbergii, ante, p. 152. 

 f In the " Hutton Collection," Newcastle-on-Tyne. 



