428 PALAEONTOLOGY OF ILLINOIS. 



concretions of Mazon creek, and both present the same appearance. Some 

 plants resembling ours have been described under the generic name of AntTio- 

 lithes. But this genus is still indefinite, and the plants referred to it really 

 unknown. I have, therefore, placed this species for description in this new 

 genus of Goppert, as more related to it by some of its characters. 



GENUS LEPIDODENDRON, Sternb. 



111. Geol. Report, rol. ii, p. 451. 



The species of this genus, as it is well known, are characterized merely by 

 the form of the cicatrices, which have been left by the base of the leaves upon 

 the bark of the trees or of their branches. These cicatrices or bolsters vary 

 indeed in size and also in their relative position, according to the thickness of 

 the different parts of a tree, where they are examined. But this variety is far 

 from being as marked as some authors, who have attempted to reduce the spe- 

 cies to two or three, seem to suppose it. In following the course of the devel- 

 opment of these scars on long stems of Lepidodendron, from parts measuring at 

 least one foot in diameter to the smallest branches, they may be seen to vary 

 in size and position according to the degree of activity of the vegetation at 

 different times, and also on account of some irregular mode of growth , but 

 their essential characters, viz. : their outline, the position of the vascular 

 points, as also the form of the leaf scars surrounding them, is generally pre- 

 served and recognizable in the whole length of the stem; It is argued that 

 for the genus Lepidodendron, we should have too large a number of species if 

 we would consider the scars as specific characters. But the genus Sigillaria, 

 so admirably studied by Prof. Brongniart, and after him by the most careful 

 Palaeontologists, especially by Goldenberg, whose acuteness of observation is 

 beyond question, has a number of acknowledged species, at least double of those 

 of the genus Lepidodendron. Goldenberg describes sixty-seven species of 

 Sigillaria I and yet the specific characters are taken from the same vegetable 

 organs, or from the cicatrices of the bark, which are certainly as much subject 

 to variations in Sigillaria as in Lepidodendron. Why, then, deny the value of 

 the species of one genus, and admit the reality of those of the other. The 

 most marked species of Lepidodendron of our American coal fields, L. modula- 

 tum, L. giganteum, L. clypeatum, L. vestitum, L. distans, published in the Geo- 

 logical Report of Penna., have been found over the whole extent of our Coal 

 Measures, and are recognized everywhere by their distinct characters from the 

 form of their cicatrices. In collecting specimens on shale, for the State Cabi- 

 net, great care has been taken in comparing the largest possible number of spe- 

 cimens of the same species at the same place, not only to obtain the different 



