346 



BRITISH GRAPTOLITBS. 



Specific Characters of Forms belonging to the Genus Retlolites. 





GROUP I = Gladiograptus. 



G. Geinitziamis. 



G. perlatus. 







var. angustidens. 





var. Daironi. 



Character of polypary 

 Reticula ..... 



Clathria ..... 



Maximum width 



No. of thecae in 10 mm. 



Sword-shape, 

 robust 



Texture thick, 



with 



sub-regular 



rounded, or 



polygonal 



meshes 



Well developed 



5 mm. 



14—9 



Uniformly 



narrower than 



typical form 



3 mm. 



Widening 

 rapidly from 

 proximal end 



Delicate and 



fibrous, with 



subrectangular 



meshes 



Very ill 

 defined 

 5 mm. 



16—12 



Very much 



larger and 



coarser than 



typical form 



p 



y 

 11 cm. 



12—8 



- 





GROUP II = Plegmatograptus. 



GROUP III = Gothograptus. 



P. nebula. 



P. obesus. 





G. nassa. 



G. spinosus. 







var. macilentus. 







Character of polypary 



Reticula .... 



Clathria .... 

 Maximum width 



No. of thecae in 10 mm. 



Cloud-like 



Irregular 



and 

 ill defined 



Indistin- 

 guishable 

 2 mm. 



12 



Fairly long 

 and relatively 



broad after 

 rapid widen- 

 ing 



Filamentous, 

 with sub-hexa- 

 gonal meshes 

 near ventral 

 margins 



111 defined 



8 mm. 



12—9 



Wide hexa- 

 gonal meshes 

 throughout 



Small and 



narrow with 



uniform 



breadth 



Conspicuous 

 meshes 

 minute 



111 defined 

 1 mm. 



1.5 



Rapidly 

 widening 



from 



proximal 



region 



Coarse and 

 irregular 



Fairly well 

 defined 

 18 mm. 



11—10 



with aper- 

 tural spines 



