1 \ x i v 



BRITISH GRAPTOLITES. 



would account for the fact that the full-grown forms do not occur in such groups 

 as do the small individuals, but are scattered among other species. 



The affinities of the Graptolites with the Pennatulidse, Sertularidae and Polyzoa 

 are discussed, and Richter concludes that they are most closely allied to the last 

 named. He adduces the rod of Rhabdopleura in support of his views, and compares 

 the thin laminae of the Graptolites to those of the cells and endocysts of a Polyzoon. 



Other points are touched upon and discussed by Richter, such as the food 

 of the Graptolites, their length of life, existence of enemies, etc., but nothing new 

 in these directions is added to the views expressed by him in previous papers. 



1871. 



Liiniarsson, 



" Om nogra Forsten- 



ingar fran Sveriges och 



NorgesPrimordialzone," 



' Kongl. Vet. Alcad. 



Forh.,' no. 6. 



In 1871, also, Linnarsson described and figured a few 

 fragments of a new species — (1) Dichograptus tenellus (Clono- 

 graptus), from the upper part of the Olenus shales in 

 Westrogothia. This was the first instance of the occurrence 

 of true Graptolites (excluding Diciyonema) in beds then 

 regarded as being of true Cambrian (Primordial) age. 



In a paper read at the Edinburgh Meeting of the British 

 Association and afterwards published in the ' Geological 

 Magazine,' Lapworth and Wilson separated the Silurian strata 

 of Roxburgh into five groups : the Hawick Rocks, the Selkirk 

 Rocks, the Moffat Series, the Gala Group, and the Riccarton 

 Beds, the last three of which are characterised by special 

 graptolitic faunas. The rich graptolitic black shales of the 

 Uplands are all referred to a single Moffat band which occurs not only in the country 

 between Selkirk and Melrose, but re-appears in the Moorfoot Hills to the north. 



In the following year, 1872, three papers were published 

 by Hopkinson. 



In the earliest of these he described a new species of 

 Oallograptus (C. radicans) from the Arenig rocks of the St. 

 David's district. He gives a full diagnosis of the genus. 



He discusses the affinities of the Dendroidea and considers 

 that while Bend/rograptus and Ptilograptus fall naturally into already accepted 

 families of the Thecaphora (or Sertularina), Callogra/ptus and Dicti/onema (the latter 

 being more Polyzoan than Hydrozoan in its affinities) should form a new family. 

 1872. 



In Hopkinson's second paper he gives a list of graptolites 

 from the Arenig rocks of St. David's. This list is preliminary 

 to the paper by himself and Lapworth, which appeared three 

 years later, when the various species were described and 

 figured. 



1871. 



Lajnvorth, C, 

 "On the Silurian Rocks 



of the Counties of 



Roxburgh and Selkirk," 



' Brit. Assoc. Reports,' 



and 'Geol. Mag.,' vol. 



viii. 



1872. 



Hopkinson, 



" On Callograptus 



radicans, a new 



Dendroid Graptolite,' 



' Geol. Mag.,' vol. ix. 



Hopkinson, 



" On the Occurrence of 



a Remarkable Group 



of Graptolites in the 



Arenig Rocks of St. 



David's, South Wales," 



[ ' Geol. Mag.,' vol. ix. 



