of the British Species and Genera of Graptolites. 355 



been found, viz. Climacograpsus teretiusculuSj a highly cha- 

 racteristic Lower- Silurian fossil. 



In the Wenlock rocks there is but one peculiar species, 

 namely Graptolites Flemingii ; G, priodon and G. colonus 

 being common but not confined to the group. The sole pecu- 

 liar species, G. Flemingii^ is only known to occur in one loca- 

 lity (Balmae in Kircudbright), in beds supposed to be of the 

 age of the Wenlock Shale. Retiolites Geinitzianus has been 

 looked upon as a characteristic Wenlock form ] but it occurs 

 abundantly, with Lower- Silurian species, in the Coniston 

 Flags, and it appears to have lived on into the Ludlow 

 period. 



In the Lower Ludlow rocks the beautiful Ptilograpsus 

 anglicus has hitherto been exclusively found, whilst in both 

 the Lower and Upper Ludlows G. priodon and G. colonus are 

 of common occurrence. 



Subjoined are tables showing the distribution in time of the 

 genera and species of Graptolitidae which have been discovered 

 in Britain. 



Table showing the Vertical Distribution of the British Genera 

 of the Family of the Graptolitidce. 



Genera. 



Dictyonema 



Dichograpsus . . . 

 Tetragrapsus . . . 

 Phyllograpsus . . . 

 Dendrogi'apsus . 

 ClimacogTapsus . 

 Diplograpsus . . . 

 Didymograpsus . 

 Pleurograpsus . . . 



Graptolites 



Rastrites 



Helicograpsus . . . 

 Cyrtograpsus . . . 



Retiolites 



Dicranograpsus . 

 Callograpsus . . . 

 Ptilograpsus . . . 



11 



u 

 P. 





25* 



