Distribution of the Rhabdophora. 337 



Dr. Tornquist has identified, in addition, Didymograptus 

 e.rtensus, Hall, Didymograptus affinis, Nich., and Phyllo- 

 graptus typus, Hall. To these Mr. Linnarsson has recently 

 added representatives of Didymograptus v-fractus, Salt., Tri- 

 chograptus multiplex, Nich., Diplograptus Hopkiasoni, Nich. 



The dark shales that succeed to the Cambrian rocks of the 

 neighbourhood of Christiania in Norway, and include the 

 local representative of the Orthoceras-Limestone of Sweden, 

 have long been known to be graptolitiferous. A few of the 

 Ivhabdophora of these beds have been figured by Boeckf and 

 Scharenberg \ ; but the horizons of the species are unknown. 

 The forms named below may be easily identified upon their 

 plates. Those in all probability restricted to the higher zones 

 I have marked with an asterisk. 



Tetragraptus fruticosus, Hall. l'hyllograptus typus, Hall. 



Didymograptus Murcbisoni, angustifolius, Hall. 



Beck* Cliniaeograptus Scharenbergi*, 

 geminus, His. Lapic. 



America. — As pointed out by Professor Selwyn§, the main 

 mass of the Point-Levis or Quebec group of the valley of the 

 St. Lawrence lies at the very base of the Ordovician or Lower 

 Silurian system, and is thus, broadly speaking, synchronous 

 with the British Arenig rocks. Its B,habdophora have been 

 long familiar to the eyes of palasontologists in the beautiful 

 plates of Hall's classical memoir on the Graptolites of the 

 Quebec Group. It may be that the more ancient of the 

 strata from which his specimens were procured may even- 

 tually be proved to be of true Cambrian age. In the mean- 

 time, however, no division of these forms can be attempted. 

 The species figured by Hall from Point Levis include : — 



Clonograptua flexilis, Hall. Didymograptus bifidus, Hall. 



rigidus, Hall. indentatus, Hall. 



abnorniis, Hall. extenuatus, Hall. 



rauiulus, Hall. constrietus, Hall. 



Loganograptus Logani, Hall. arcuatus, Hall. 



Dichograptus octobrachiatus, Hall. extensus, Hall. 



Tetragraptus Headi, Hall. penuatulus, Hall. 



alatus, Hall. Phyllograptus typus, Hall. 



crucifer, Hall. iliciformis, Hall. 



quadribrachiatus. Hall. angustifolius, Hall. 



denticulatus, Hall. Diplograptus dentatus, Brongn. 



bryonoides, Hall. inutilis, Hall. 



Bigsbyi, Hall. Climacograptus antermarius, Hall. 



Didymograptus nitidus, Hall. Trigonograptus ensiformis, Hall. 

 patulus, Hall. Ketiograptus tentaculatus, Hall. 



t Boeck, ' 15ema3rkninger angaaende Graptolitberne : ' Cbristiania, 1851. 

 | Scharenberg, 'TJeber Graptolithen:' Breslau, 1851. 

 § Selwyn, Canadian Naturalist, 1870, p. 17. 



