4 54 PALAEONTOLOGY OF ILLINOIS. 



strangulated or narrowed into a broad, tubulous, plaited leaf? 

 or stem ? resembling a large leaf of Stigmaria. It may indi- 

 cate the first development of a rootstock, or represent a tuber- 

 cle like those found at the end of the leaves of Stigmaria. 

 It is marked in its upper part by a large round mammillate 

 cicatrice, resembling also that of a Stigmaria. Its peculiar 

 form cannot be considered as some casual deformation, as it is 

 not only distinct in the middle of a concretion, but we have 

 two specimens of exactly the same conformation. The one 

 which is not figured has the leaf longer, and the tuberule 

 slightly smaller. 

 From Mazon creek. 



STIGMARIOIDES VILLOSUS, Sp. nov. 



PI. xxxi, fig. 1. 



THE form of this kind of tubercle is about the same as 

 that of the former species, square, round in outline, appearing 

 to have been cylindrical or inflated. Its surface is marked by 

 two kinds of cicatrices: the one, numerous, punctiform, infla- 

 ted, placed close to each other in irregular spiral order ; the 

 other much larger, auricular, with a mammilla and central 

 point. The first look like scars of scales, the others like those 

 of rootlets. This tubercle is, as seen on the figure, in close 

 connection with a branch of Pecopteris villosa, Brgt. 



But the union of both parts is not evident, for at its base the rachis is 

 straight, and not curved to the root, by which the juxtaposition may be casual. 

 Nevertheless the verrucoee surface of the tubercle resemble so much that of 

 the stem of the Pecopteris villosa, that it is scarcely hazardous to consider it as 

 part of the rhizoma of this fern, and the same familiar juxtaposition of the 

 same species of fern and the tubercle is marked upon the three specimens, 

 which are all that have been procured as yet of this peculiar form. 



Found at Mazon creek, in concretions of argillaceous iron ore. 



