436 PALEONTOLOGY OF ILLINOIS. 



But there is a difference worth mentioning. M. Brongniart 

 says that the leaves are coriaceous and very smooth; while in 

 our specimens the surface is evidently rugose, as if it had been 

 originally squamose or hairy. On a specimen in the Cabinet 

 of Amherst College, the surface of the leaflets appear perfectly 

 smooth and the veins deeply marked, thus agreeing exactly 

 with Brongniart's description. The difference is probably 

 casual, and caused by a more or less prolonged masceration of 

 the plants, before the solidification of the shales. The Illinois 

 specimens are from Colchester (coal No. 3), and the fern has 

 preserved its epidermis transformed into a thin coat of coal. 

 The specimen at Amherst has a naked surface. 



Sphenopteris abbreviata, Lsqx. Qeol. JRept. Penna., p. 861, 

 tab. 9, fig. 1 and 1 b. Mazon creek ; a small specimen. 



Genus Hymenophyllites, Gopp. Frond membranaceous, 

 many times regularly pinnately divided or irregularly cut, lobed 

 with pinnatifid or dichotomous divisions decurring on a broad 

 common rachis, which is sometimes indistinct; veins pinnate, 

 percurrent, solitary in each division. 



Hymenophyllites pinnatifidus, Sp. nov. PL 34, fig. 2 and 2 a. 

 Frond tripinnate; primary pinnse large, with divisions alter- 

 nate and open, perpendicular on the smooth round rachis ; 

 secondary pinnae lanceolate, with alternate ovate-lanceolate 

 short pinnules, which are also pinnately parted in ridge-shaped 

 divisions. These are generally cut in two or three lanceolate, 

 obtuse lobes, the terminal one simple and small. The species 

 is related to Hymenophyllites Hildrethi, Lsqx., Geol. Rept. Penn., 

 p. 863, tab. 9, fig. 5 and 5 a, differing from it by the ramifica- 

 tion, the shorter and more obtuse lobes, etc., and also (but dis- 

 tantly) to /Sphenopteris lanceolata, Gutt. Abundant at St. John 

 and Colchester, in the roof shales of coal No. 3. 



Hymenophyllites spinosus [Sphenopteris), Goppt. Oattg. Foss., 

 pi. 3-4, p. 70, tab. 12. This very fine and rare species is 



