HAHX, DIGTYONEMA-FAUNA OF NAVY ISLAND, N. B. 145 



thecse. These nepiastic stages of Dictyonema are characterized by the 

 large angle of divergence of the first theca, the next following tripod 

 aspect, particularly by the 1-branch-stage fairly symmetrical and basket- 

 like (compare figures on plate XXI), while Staurograptus has the first 

 bud apically derived and mostly appressed and passes afterwards through 

 a characteristic stage with six branchlets resting in a plane vertical to 

 the axis of the sicula. It further exhibits a slight asymmetry because of 

 accelerated divisions of one of the primary branches. The following 

 neanastic stage develops not only wholly the specific features, but even 

 some of varietal value, while nemas become rare. In D. flabelliforme 

 var. acadica, a subsequent dividing of the co-equal four primary branches, 

 happens after this, though on one or the other retarded branch 3, 1 or 

 even 6 thecae may form a uniserial twig before its division. (Compare 

 figure 2 on Plate XXI.) 



The first dissepiment, being the last appearing generic feature, is de- 

 veloped as a rule when branches of the third or fourth order are present.. 

 Thus very often a lateral compression of the movable branches will 

 furnish a striking bryograptoid view. The same is true in var. conferta,. 

 besides the fact that with the latter a monopodial dividing frequently 

 occurs. The neanastic stages of var. ruedemanni, however, are charac- 

 terized by irregularly crowded branching and early appearance of cross- 

 threads, as fully described and figured ((1), plate 1, figs. 13 to 19) by 

 Euedemann. Beyond that, several of the neanastic specimens of this. 

 variety prove to be so much accelerated, that immediately from the sicula 

 a thick scarcely resolvable bush of rhabdomes appears to arise in a real 

 dendrograptoid manner of growth. Xeanastic stages of var. norivegica 

 and var. desmograptoidea do not deviate from those of the forma typica 

 except in one specimen of the latter variety, which has the irregular- 

 division of the branches at a remarkably large angle somewhat acceler- 

 ated. 



Staurograptus dichotomus generally runs through a 5- or 7-b ranch- 

 stage and the individuals of this collection turn into var. aperta by slow 

 or retarded dividing of an angle of 70° to 90°. 



The ephebastic stage of Dictyonema fabeUiformer chiefly establishes 

 the characteristic outline of the colony which is infundibutiform in var. 

 acadica, norivegica, ruedemanni and desmograptoidea, pyriform in ruede- 

 manni m. f. conferta and vasiform in conferta. It is in this stage that 

 the essential features of variety desmograptoidea and norivegica are fully 

 developed. Basal expansions are now more commonly found. The ephe- 

 bastic stage of Staurograptus, relatively rare, regarding the surplus of 

 younger individuals, shows a diminution of the angle of divergence, en- 



