1872.] KICHOLSOlvr MIGEITIONS of the GHAPXOLITEd. 227 



as Scotland itself is concerned, a considerable number of the Uijper 

 Llandeilo Graptolites continued to exist in their own area, though a 

 stiU larger number became extinct. The remains of those which 

 survived are found in a great series of rocks superior to the Dum- 

 friesshire Shales and also to the Bala Limestone (Wrae Limestone), 

 to which their discoverer, Mr. Charles Lapworth, applied the name 

 of the " Gala Group." Regarding the Gala group, for the present, 

 as a single series of deposits, the following Table exhibits the chief 

 Graptolites which are known to occur in it. 



Graptolites of the Gala Group. 



Climacograpsus teretiusculus, His. ^ 



Diplograpsus pristis, His. ' 



Eastrites LinnsBi, Barr. 



Graptolites Sedgvvickii, Porfl. . Derived from the Upper Llandeilo of 



Nilssoni, JBarr. | the Scotch area. 



■ lobiferus, iii' Coy. I 



sagittarias, His. \ 



Eetiolites perlatus, Nich. j 



Graptolites exiguus, Nich. \ 



priodon, Bronn. \ 



colonus, Barr. )■ Derived from the Couistoa Mudstones. 



tiirriculatus, Barr. \ 



Eetiolites Geinitzianus, Barr. J 



It appears from this list that the Gala group has yielded thirteen 

 Bpecies of Graptolites, of which eight, or over sixty per cent., are 

 identical with species of the preexistent L'"pper Llandeilo area. The 

 diprionidian species of the genera Climacograpsus and Diplograpsus 

 I give on tho authority of Mr. Lapworth ; but they have not come 

 under my own notice, and they seem to be certainly absent from the 

 higher part of the Gala Group. "We have also to notice the absence 

 in the Gala group, as in the Coniston Mudstones, of any represen- 

 tatives of the genera Didymograpsus , Dicranograpsus, Ccenograpsus, 

 and Pleurograpsus. The remaining five species of the Graptolites of 

 the Gala group are not survivors of the Upper Llandeilo fauna, but 

 are all found in the Coniston Mudstones, and appear, therefore, to be 

 importations from the Coniston area of the jSTorth of England. 



The data at present in my possession do not enable me to speak 

 positively as to the further career of the Graptolites of the Gala 

 group. So far as is known to me, the only survivors of this period 

 were G-rap>tolites colonus, G. priodon, and Uetiolites Geinitzianus, of 

 which the tvv'o former occur in the Wenlock rocks of Kirkcudbright- 

 shire, whilst the two last mentioned occur in the Ludlow rocks of 

 the Pcntland hills. 



E. HuDSON-EivEK AiiEA OF NoRin Asii=:pacA. — The greatest migra- 

 tion of the Upper Llandeilo Graptolites of the south of Scotland 

 appears to have taken a westerly course, and to have ultimately 

 reachei the United states, forming the well-known Graptolitic fauna 

 described by Hall as occurring in the Hudson-River Shales and Utica 

 Slates (Caradoc). 

 . The grounds for this belief I will state immediately ; but I may 



