STUDY OF THE GRAPTOLITES. 



235 



is described as dividing, from a short and slender base, " into two stems, 

 each supporting the cells on their upper sides." " Branches are given off 

 at irregular intervals from these principal stems." In the Intellectual 

 Observer (No. Ixv, 1867), Mr. Carruthers has given the following 

 description of the genus: 



^^ Cladog7'apsus, Car. Polypary compound; growing bilaterally from 

 the primary point ; irregularly and repeatedly branching and rebranching, 

 and without a central disc." 



The original figure illustrating Cladograptus linearis (Annals & Mag. 

 of Nat. History), shows it to be a fossil belonging to the group of G. gra- 

 cilis (Hall), and the figure of the same in the Intellectual Observer 

 shows less distinctly the same characters. The form is not branching and 

 rebranching in the ordinary acceptation of that term, as is clearly enough 

 shown in the figures of Mr. Carruthers. In the figure first cited the two 

 main parts diverge on two sides from an initial point, and the divisions on 

 one of those parts or branches rise at regular intervals from one side of 

 the common rachis. In the specimen figured, the stipes or offshoots are in 

 two pairs and at equal distances from each other, the intervening space 

 being about three times as great as between the individuals of each pair, 

 and probably indicating the place where two others have been broken off. 

 In the American species of this type, there are no cellules on the principal 

 rachis, except towards the distal extremities of the two parts, and beyond 

 all the subdivisions, which are usually from one side only. 



Cladograptus linearis, Carruthers. 



In the figure of C. linearis given in the Intellectual Observer, the 

 divisions are shown as originating from one side only, while the main axis 

 is continued, but not to our view branching and rebranching as described ; 

 not at least in the sense in which we apply that term to such forms as 

 G.flexilis of this paper, or to such forms as Dendrograptus. There is no 

 division of the celluliferous parts of the stipe, if we may judge from 

 analogy with similar forms in the American rocks. 



Should the term Cladograptus of Geinitz be retained for certain forms 

 as suggested above, then the Oenus Cladograptus of Carruthers must 

 be abandoned; and in any event it can scarcely be continued, since the 

 same generic term had been previously applied to other forms of graptolites, 



