EXPLANATIONS OF PLATE IV. 

 Phylloqraptus iltcifolius. 



Fi's- 1- An enlarged figure of a compressed specimen, showing the faces of two 

 adjacent folia ; the margins being broken away so as to show the cell- 

 openings. 



" 2. A specimen of the natural size, where one folium is broken awaj', not quite so 

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



" 3. A specimen compressed in the same manner as figs. 1 and 4; the upper folia have, 

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

 the middle 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). 



" 4. An enlargement of a specimen which is imbedded obliquely, as in fig. 1, or in a 

 direction as if the theoretical figure 5 were vertically compressed, leaving 

 no visible axis. In the lower half of the specimen tjie fossil has been sepa- 

 rated 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 cellules 

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

 conspicuous (enlarged to three diameters). 



*' 5. A restoration of the form of P. ilicifolius, showing the four divisions ; 

 which are represented as cut through transversely, exhibiting the cell- 

 cavities. 



Phyllograptus anna. 



Fig. 6. A specimen with the folia obliquely compressed. 

 " 7. An enlargement from a specimen where the two lateral folia remain, showing 

 the bases of the cells of the division which has been broken ofi" in the sepa- 

 rated laminae of the slate- The surface is distinctly striated. 



Retiograptus tentaculatus. 



Fig. 8. An individual of the natural size, with the marginal reticulations nearly entire. 



Retiograptus eucharis. 



Fig. 9. An illustration of a compound form of the genus, enlarged to font diameters. 



Dendrograptus fruticosus. 

 Fig. 10. A frond which is apparently nearly entire. 



Dendrograptus gracilis. 



Fig. 11. An enlargement from one of the branchlets, showing the striate surface and 

 the deep indentation of the cellules. 



Dendrograptus ? (Callograptus ?) diffusus. 



Fig. 12. An enlargement showing the cell-apertures. The specimens are extremely 

 compressed. 



Callograptus salteri. 



Fig. 13. Fragment of frond showing the ncncelluliferous side. 

 " 14. An enlargement from the noncelluliferous side, showing a few transverse 

 dissepiments at irregular intervals (figure enlarged). 



