236 



REPORT ON THE STATE CABINET. 



character is particularly observable ; and in a few species, the earlier 

 cellules are raised in a scarcely perceptible elevation above the general 

 surface of the common envelope. Indeed, in a few instances, it is 

 impossible to ascertain satisfactorily whether these earlier prominences 

 are expanded into open cellules. As the stipe is extended they become 

 gradually more and more prominent, until towards the middle, or oftener 

 perhaps nearer the distal extremity, their greatest degree of development 

 is reached. In some species this takes place near the base, and in the 

 more elongated stipes there is no sensible increase throughout a great 

 part of their length, and the two margins of the stipe are essentially 

 parallel. Towards the distal extremity there is a gradual, or often a 

 more abrupt, diminution in the size of the cellules; and a few of the 

 last ones are much smaller, until the terminal cellule is sometimes seen 

 in a partially developed condition between the common body and the 

 partition of the preceding cellule. 



The same condition of development in the cellules is true of the 

 diprionidian forms, as is shown in some degree in G. pristiniformis ^ Plate 

 xiii {Canadian Decade ii), but more especially in the accompanying 

 enlarged figures of G. pristis and G. whitfieldi^ the last of which also 

 shows the higher cellules diminished, so as to contract the width of the 

 stipe above (figs. 31 and 32). 



In Retiolites and Retiograptus, the full development of the cellules 

 takes place below the middle of the length of the stipes, 

 while they are less developed towards either extremity- 

 In some species of Retiolites, including one from 

 the Clinton formation, the cellules acquire their full 

 development near the base, and the margins are essen- 

 tially parallel for the greater part of their length. 



In Phyllograptus, the lesser development of the 

 cellules at the base of the stipe is a marked feature. 

 They increase rapidly towards the middle; and their 

 greatest development is sometimes above and some- 

 times below the middle, but in all cases they suddenly 

 decrease towards the apex. 



In Dendrograptus, where we have a stout stem with- 

 out cellules, the branches usually begin at some dis- 

 tance above the base, and in their lower part they have 

 scarcely the appearance of being celluliferous : in the 

 middle of their extent the cellules become more dis- 



FiG. 31. 



Fig. 32. 



