180 



TWENTIETH REPORT ON THE STATE CABINET, 



Fig. 18. Fig. 19. 



Gravtolithus (Ccenograptus) gracilis.* 



We have still another group, presenting some differences, more particu- 

 larly in the development and form of cellules, than in their general features 

 or mode of growth ; and seeming in some species to unite the characters of 

 tiiose having a single range, with those having a double range of cellules. 

 The simpler forms of this type are tsimilar to the two-stiped forms of the 

 first series ; but in all those, whether of two, four, or more stipes, the 

 cellules are developed on the upper sid'e, or that side opposite to the initial 

 point. In species like G. sexta?is, G. divaricatus, and others of this type, 

 the cellules are on the lower, or same side with the initial point or radicle. 

 For these forms I have proposed the name Dicranograptus. 



Fig. 20. 



Graptolithus (Dicranograptus) divaricatus, and enlargement of cellules. 



In the accompanying figure of G. divaricatus, the frond consists of two 

 simple uniserrate stipes ; and the same is true of G. sextans, except that 

 it is united at the base for the length of a single cellule. In G. furcatus^ 

 the stipes are conjoined for a distance of two or three cellules above 

 the base. 



* The fig. 19 was theoretically constructed, but has since been verified by the discovery 

 of a specimen having the same form and arrangement of parts. 



