EXPLANATIONS OF PLATE XVL 



Phyllograptus iLiciFoiiius, page 121. 



Fig. 1. An individual of the natural size, where the folia b, a* are broken entirely 

 away beyond the axis, leaving the bases of the cellules of two adjacent 

 folia visible, except at the upper part of the figure, where two or three of 

 the bases of the other cellules remain. 



" 2. A similar specimen, showing the bases of a set of cellules on each side of the 

 centre, with two or three of those belonging to the broken folium at the 

 base of the figure. 



" 3. An enlargement of fig. 2, showing more distinctly the cellules on each side 

 of the central line, and the small remaining portion at the base. 



" 4. A specimen of the natural size, where one' folium is broken away not quite 

 so far as the axis, leaving the bases of its cellules visible. 



" 5. An enlarged figure from a specimen which has been imbedded transversely. 

 Three of the divisions have been broken away, leaving impressions of the 

 lateral ones only, and of the cell-bases and cell-partitions of the fourth 

 division, which are directed obliquely upwards from the axis and point of 

 view. The lower part of the specimen preserves a portion of the lateral 

 folia, with tlie bases of the cells of the outer division a*, which are directed 

 towards the axis. 



" 6. An enlargement of a specimen which is imbedded obliquely, or in a direc- 

 tion as if the theoretical figure 10 were vertically compressed, leaving 

 no visible axis. In the lower half of the specimen, the fossil has been 

 separated in the opposite slaty laminae, leaving only the impression of that 

 side, which also shows no axis. In the upper half of the specimen, the cel- 

 lules are well preserved, and on the left-hand side the apertures are con- 

 spicuous. Enlarged to three diameters. 

 It will be observed that the impression is not quite in the same direction 

 as the outline in the upper portion of the figure, owing to the obliquely- 

 compressed folia. 



" T. A specimen compressed in the same manner as fig. 6 ; the upper folia have 

 however been separated, except the bases of a few of the cellules in the 

 upper part of the figure, leaving the other two folia imbedded in the shale, 

 and showing the bases of their cellules ascending from the axis. Enlarged 

 to three diameters, as in fig. 6. 



" 8. An enlarged figure of a specimen compressed in the direction first described, 

 without any separation of the parts ; from which cause there is no proper 

 axis visible. In this condition, the specimens resemble Graptolitkus folium 

 of Hisinger, or G. ovatus of Barrp.nde. 



" 9, An enlargement of a specimen compressed as in fig. 8, but with the cellules 

 filled, and the margins of the upper two folia broken, showing the cell- 

 openings. (8 and 9 are enlarged to twice their natural size.) 



" 10. A restoration of the form of P. illcifolius, showing the four divisions ; which 

 are represented as cut through transversely, exhibiting the cell-cavities. 



* These letters refer to the illustrative figures, page 119. 



