430 On the Geological Distribution of the Rhabdophora. 



[f) Zone with Dicranograptus Clingani, Carr. 

 This is locally prolific in the British forms 



Diplograptus foliaceus, Murch. Lasiograptus, sp. n. 



quadrimucronatus, Hall. Dicranograptus Clingani, Carr. 



Climacograptus bicornis, Hall. DicellograptusForchhamrnerijGWn. 



• caudatus, Lapw. Morrisi, Hopk. 



(g) Zone of Orthis argentea, His. 



The only species noted from this zone is an undetermined 

 form of Climacograptus. 



These results harmonize the data previously collected from 

 the district by former observers*, and are in strict concordance 

 with the little that is yet known respecting the fossils of the 

 corresponding strata in Westrogothia, Dalarne, and the island 

 of Bornholmf. 



The zones (a) and (b) represent those British strata which, 

 pending the advent of a more suitable title, we may term the 

 Passage-beds between the Arenig and Llandeilo formations. 

 The zone (a) is essentially Arenig in its general facies. The 

 zone (b) is the exact representative of the Lower Llandeilo or 

 Murchisoni-zone of Abereiddy Bay. The zones (c) and (d) 

 are, as Linnarsson remarks, distinctly of Llandeilo age. 

 Zone (e) is probably the equivalent of the transitional Glen- 

 kiln shales of South Scotland. Zones (/) and (g) are, as 

 Linnarsson observes, the Swedish representatives of the main 

 mass of the Hartfell shales, and are therefore of unequivocal 

 Bala age. 



The highest strata of the Swedish Ordovician are the so- 

 called Trinucleus- Schists. The only Graptolites they have 

 yielded hitherto are % 



Diplograptus pristis, His. Dicellograptus elegans, Carr. 



America. — The Hudson-River group or Lorraine Shales of 

 New York and Canada, and their western representative the 

 Cincinnati group of Ohio, occupy the systematic place of the 

 British Caradoc rocks. Only a few Graptolites are yet known 

 from these beds. From the Cincinnati group Hall enu- 

 merates § 



Climacograptus bicornis, Hall. Diplograptus putillus, Hall. 

 typicalis, Hall. 



* Tornquist, GEfvers. af K. Vet. Akad. Fbrh. 1875, no. 10, 4; Linnars- 

 son, Geol. Fbren. no. 22, 1875, &c. 



t Johnstrup, Forh. Skand. Naturf. 11 (Copenhagen, 1873), pp. 

 305-308. 



X Conf. Linnarsson, Geological Magazine, June 1876. 



§ Hall, Grapt. Quebec Group, p. 44, &c. 



