42 On Variations of Sigillarke. 



ciently preserved to show the variation of the leaf scars in 

 different individuals of the same species, or even upon different 

 parts of the same individual. Yet the great majority of 

 species have heen constructed upon a few fragments, and 

 many even from a single isolated fragment of bark, or its im- 

 pression. It will doubtless be forever impossible to determine 

 all the species accurately. But the means are constantly 

 increasing, and ought now to be sufficient to permit the elimi- 

 nation of manj" of the false species. M. Schimper has already 

 begun in this branch of Palaeontology the synthetic phase. 

 But as regards the fossil plants of America, the change is 

 almost entirely yet to come. 



It is the purpose of the writer to show, in a series of brief 

 papers, the variations and relations of some of the common 

 forms of Lepidodendron and Sigillaria that have come under 

 his observation, with the object of helping, if possible, the 

 determination of the true species. 



The first of the present papers will relate to variations in 

 the leaf-scars of certain common Sigillarise; the second will 

 endeavor to prove the identity of several so-called species of 

 Lepidodendron. 



Wo. 1. — On the Variations of the Decorticated Leaf-scars of 

 certain Sigillarice. 



(With Plates III and IV.; 

 Read June 4, 1877. 



The sub-cortical scars of Sigillaria reniformis, Brogniart, 

 and of 8. laevigata, Brgt., present remarkable variations in 

 size and form, even npon small surfaces of the trunk. One 

 strange form of 8. reniformis has been described and figured 

 by Prof. L. Lesquereux, in Rogers' Report of the Geology of 

 Pennsylvania, as a distinct species, under the name of 8. 

 discoidea. After the description he comments as follows: 

 u * * * it s place in the family of the Sigill arise is scarcely 

 acceptable. But as we could not obtain any good specimens 

 for further examination, we have nothing else to say about its 

 other characters ; we mention it here till some better opportu- 

 nity to study it is afforded." 



