i»>0 



m:\\ h>i:k m a I h MUSIXM 



aud, like 1 ) i c h o ji: r a p t u s o c t o b r a e h i a t u s and 

 Tetragraptus, reached a staj^'e with a tixed aud more limited 

 Dumber of braiuhes. This form would then stand at the 



Fig. 11 Idem. Mature hydrosome. Shows the restricted number of 

 branches (24), in this variety. Nat. size 



end of the Goniograptidae, as far as the genus is known, and 

 might be designated as Goniograptus thureaui var. 

 postremus. 



The important ontogenetic and morphogenic facts of which 

 this series of growth stages permits a statement are: 



1 The ''funick'^ of Gonwgraptus consists of two thecae. The 

 equal length of the two parts of the funide between the 

 sicula and the first dichotomy and of the primary branches 

 in the other multiramose dichograptids indicates that the 

 funicle is in all these constructed of two thecae. ' With ad- 

 vancing growth of the colony, the two thecae of the funicle, 

 like those of tin- principal stems, become greatly thickened 

 and assume the form of cylindric stems, thus more or less 

 losing indications of their former thecal nature (fig. 10 and 

 111. The statement, found from Hall's work onward in nearly 

 all descriptions of the colonies of these multiramose dichograp- 



