MODE OF GROWTH AND DEVELOPMENT OF 

 GONIOGRAPTUS THUREAUI McCoy 



BY RUDOLF RDEDEMANN 



In 1889 1 Dr Ami announced the occurrence of G o n i o - 

 graptus thureaui in the Tetragraptus zone of Levis, 

 Quebec. This remarkably pretty graptolite, the generic type 

 and only species of the genus Goniograptus, was till then 

 known only from the graptolite beds of the Bendigo gold 

 field, Sandhurst, Victoria, Australia, whence it was described 

 by McCoy. 2 It is there, as in the Levis and Deep kill beds, found 

 associated with the species characteristic of the Tetragraptus 

 zone. Dr Ami figured a remarkably large and perfect specimen 

 and added the description of the central disk which extends in 

 a peculiarly alate manner along the branches. 



In the Deep kill section numerous hydrosomes of this 

 species have been found, not only in the Tetragraptus zone, but 

 also in the beds of the overlying zone with Didymograp- 

 tus bifidus. and Phyllograptus ainna. The ma- 

 terial from the former zone proved to be of special interest for 

 the study of the ontogeny of the species, for it contained a com- 

 plete series of finely preserved growth stages from the sicula 

 onward to the mature colony. These stages allow the elucida- 

 tion of some points in the ontogeny and morphology of the mul- 

 tiramose dichograptids which were hitherto not well under- 

 stood; and they have therefore been made the subject of this 

 notice. 



A restricted number of characteristic stages has been figured. 

 The outlines of the figures have, with one exception, been drawn 

 with the camera lucida and reduced to their present size. 



Sicula. The sicula itself is rather short and stout, as those 

 of many other dichograptids; it can, therefore, when alone, be 

 hardly distinguished from the siculae of several other species 

 occurring in the same beds. 



'Can. rec. sci. 1888-89. 3:422, 502. 



2 Ann. and mag. nat. hist. 1876. p. 128; Geol. Sur. Victoria. Prodi*, pal. 

 Victoria. Decade 5. 1877. p. 39. 



