206 



REPORT ON THE STATE CABINET. 



portions of fronds, which, presenting in the different species great varie- 

 ties of form and aspect when entire, are nevertheless composed of parts 

 so similar that these fragments, though indicating specific differences, 

 offer little clue to a knowledge of the entire form. 



Taking these species which, in the form of their cellules and in the 

 separated fragments of the frond, would be referred to Graptolitlms proper, 



Fig. 4 



Fis. 5. 



and tracing them, as we are now able to do in many species, to their 

 perfect condition, we find a great variety of form and mode of growth. 

 In the simplest of these, we have two stipes diverging from a radicle 

 or initial point; and the parts remain so complete as to admit of no 

 doubt that this is the entire skeleton of the animal. The cellules near 

 the base of the stipe are not so fully developed, while also those near the 

 extremities have not reached their full dimensions ; and the last one 

 is sometimes barely perceptible, or just assuming its form from the 

 common body. These characteristics are perceptible in figure 2 of Grap- 

 tolithus (Didymograptus) pennatulus. 



