SUPPLEMENT. «0a 



The species of this genus approach in general form to G. ovatus of Barkakde 

 and G. folium of Hisinger. They present, however, some differences of character; 

 varying from broad -oval with the extremities nearly equal, to elongate -oval or 

 ovate, the apex usually the narrower, but in a few instances the base is narrower 

 than the apex. These forms are sometimes extremely numerous in the shales, and 

 present on a cursory examination a general similarity to the leaves of a large 

 species of J^europteris in the shales of the Coal measures. 



Instead of the narrow filiform midrib represented in the figures and descriptions 

 of the authors mentioned, these specimens present a broad linear midrib continued 

 from the apex to the base, and extended beyond the base in a slender filiform ra- 

 dicle, usually of no great extent, but in some instances nearly half an inch in length. 

 The midrib is rarely smooth, varying in width, with its margins not often strictly 

 defined. In examining a great number of individuals of one species, I have dis- 

 covered that this midrib is serrated; and though for the most part the serratures 

 are obscure, they nevertheless present all the characteristics which they exhibit in 

 graptolitcs of other forms, in which the branches have been compressed vertically 

 to the direction of the serratures. 



1 A 3. Phyllograptos typos in two extreme fomu. 



In this view, the lateral leaflike portions appear to be appendages to the central 

 serrated portion; but these are nevertheless denticulate on tlieir margins, and the 

 intermediate spaces are well defined, as if admitting of no communication by ser- 

 ratures or cellular openings with the centre. 



In another species the central axis or midrib is strong and broad, often prominent 

 and distinctly serrate; the edges of the interspaces being all broken oflF, as if the 

 extremities had been left in the slate cleaved from the surface : at the same time, 

 the lateral portions are so well preserved as to show distinct cellules upon each 

 side. We have therefore three ranges of cells visible, the central axis projecting at 

 right angles to the two lateral parts. This remarkable feature leads to the inference 



f PALiEONTOLOOT III.] 64 



