of the Fossil Plants of the genus Sigillaria. 65 



page 104 ; it has nine arms, five of which subdivide into two branches, 

 at about eighteen inches from the centre of the fossil, and one at three 

 feet ; in this, as in the other instance, they are all broken off short." * 

 But the branches — what connection have they with the specimen upon 

 which they rest ? This is a question that does not appear to have been 

 sufficiently attended to when drawing up the description just quoted. 

 From^the remark elsewhere made, that Stigmaria was "of a yielding 

 fleshy substance, with numerous arms, proceeding on all sides from a 

 central dome,"t one would be induced to suppose that the *^'arms" oi 

 the convex specimen grew out from the margins of the " central por- 

 tion." I cannot agree to this, because the specimen affords no evidence 

 in support of it ; on the contrary, nothing is more easy to prove, than, 

 that the arms or branches had no other connection with the specimen but 

 that of superposition. The proving of this may be effected by simply 

 removing the branches, when it will be seen that the markings on the 

 channels are perfectly continuous with the wrinkles on the central por- 

 tion : were it as is generally supposed, the wrinkled part would here 

 and there display a fractured surface, arising from the breaking off of 

 the branches. 



From what has just been said, it is evident that the markings on the 

 central portion of the convex specimen have been produced in the same 

 manner as the scars and wrinkles on the channels ; or, in other words, 

 that they are merely impressions which have been derived from a super- 

 imposed body : in short, it follows, that this specimen is nothing more 

 than an indurated mass of mud, precisely similar to what must have 

 occupied the hollow or under surface of the fossil represented in plate 

 31, fig. 2, of the " Fossil Flora;" and, that the branches are portions of 

 a Stigmaria which originally rested upon it, and which probably still 

 remains fixed in the roof of the pit. 



The explanation which has been given, there is every reason to sup- 

 pose, would not have been required, but for the fact, that the branches 

 have undergone so much compression, especially at their upper extre- 

 mity, as to produce the appearance as if they had grown out from the 

 sides of the specimen, and as if the markings on their upper surface 

 were continuous with the wrinkles on the crown. I am fully per- 

 suaded, it is entirely through this deceptive appearance that Lindley 

 and Hutton have been led into the belief that Stigmaria had a dome- 

 shaped centre, from which numerous arms proceeded on all sides. 

 Agassiz also appears to have been misled in the same manner.j 



Another point remains to be disposed of. From the " ideal vertical 

 section," which is given in plate 31, figure 2, of the " Fossil Flora," it 

 might be concluded that Stigmaria had a rounded or convexly formed 

 upper surface The untenableness of this conclusion will, however, be 



» " Fossil Flora," vol. ii. preface, pages xiii. and xiv. f Ibid. p. xv. 



X Translation of the '• Bridgewater Treatise." 

 VOL. XXXVII. NO. LXXIII. JULY 1844. E 



