xlvi 



BRITISH GRAPTOLITES. 



external resemblance of Dictyonema to Fenestella. He adds, " The presence of the 

 projecting Graptolite cells, and horny texture, however, prevents its being con- 

 founded with that genns ; but the resemblance is very close, and I think we have 

 here a real affinity." 



He discusses the geological age of the Skiddaw slates as evidenced by their 

 included Graptolite species, and compares them with the beds of the Quebec 

 group. 



In the two reports of Logan on the " Geology of Canada," 

 which appeared in 1863-4, Graptolites are referred to, but 

 nothing is added in them to our previous knowledge of the 

 group in general. 



They are stratigraphical in their bearings, and Logan dis- 

 tinctly recognises the probable identity in age of the Norman's 

 Kill shales and the Utica and Hudson River groups on the ground of the 

 similarity of their Graptolites. 



1863-4. 



Logan, 

 ' Geology of Canada," 

 and " Graptolites of 

 the Quebec Group, " 

 Reports of Progress.' 



1863. 



Dewalque, 



" Notes sur les Fossils 



Siluriens de Grand 



Manil," ' Bull, de la 



Soc. Geol. de France,' 



ser. 2, vol. xx. 



Dewalque recorded in 1863 the occurrence of certain 

 " scalariform impressions " of Graptolites (identified by 

 Barrande) in the Silurian shales of Grand Manil, Belgium, 

 but no names were given. 



In the same year Billings again discussed the question of 

 the age of the Quebec group, as evidenced by its included 

 Graptolites. He concludes that it must lie between the 

 middle of the Oalciferous group, and the bottom of the Black 

 River limestone. As regards the identity in age of the Chazy 

 and the Quebec groups, he considers (from the dissimilarity 



in the species) that in a " portion of the Quebec group we have a set of strata 



representing those which are absent (elsewhere) in Canada." " The remainder 



may possibly be of the age of the Chazy." 



In 1864-5 Tornquist described and figured six species 

 from the Swedish Lower Silurian beds of Fagelsang. These 

 are (1) Diplograpsus teretiusculus (probably including also 

 Glimacog. Scharenbergi), (2) Phyllograptus typus, (3) Didymo- 

 grapsus Murchisord, (4) Dendrograpsus gracilis (considered 

 by Holm to be a Pterograptus), and a new species (5) Didy- 

 'S virgulatus. Finally he gives examples of (6) Dictyonema fldbellif or me, 



showing flic structure of the branches. 



1863. 



Billings, 



" Parallelism of the 



Quebec Group, etc.," 



' Geol. Survey of 



Canada.' 



1864-5. 



Ti'irnquist, 



" Om Fagelsangs- 



traktens Undersiluriska 



Lager," ' Luuds Univ. 



Arsskrift,' torn. ii. 





