j$36 Mr. C. Lap worth on the Geological 



Dichograptus octobrachiatus, Hall. Didyinograptus bifidus, Hall. 



Sedgwicki, Salter. Nicholsoni, Lapw. 



Tetragraptus Headi, Hall. affinis, Nich. 



quadribrachiatus, Hall. Phyllograptus typus, Hall. 



bryouoides, Hall. angustifolius, Hall. 



crucifer, Hall. Diplograptus Ilopkinsoni, Nich. 



Didymograptus patulus, Hall. inucrouatus ?, Hall. 



gibberulus, Nich. Azygograptus Lapworthi, Nich. 



nitidus, Hall. 



The various species of Monograptus (Graptolithus*) quoted 

 by Salter and others from the Skiddaw series are almost cer- 

 tainly merely fragments of compound genera. The Grapto- 

 lithus latus of M'Coy f was certainly of this nature ; and the 

 Graptolithus tenuis, G. Nilssoni, and G. Sagittarius of Salter 

 may with safety be assumed to have had a similar origin. 

 His Didymograptus sextans (Dicellograptus?) is equally dubi- 

 ous. His Diplograptus pristis could not have been Hisinger's 

 species, but was possibly Diplograptus serra (Brongn.) or 

 some allied biserial form. 



From the Upper Arenig rocks of Ellergill &c. Professor 

 Nicholson has collected % : — 



Trigonograptus lanceolatus, Nich. Didymograptus geruinua, His. 



Trichograptus fragilis, Nich. fasciculatus, Nich. 



Didymograptus patulus, Hall. Glossograptus armatus, Nich. 



bifidus, Hall. Phyllograptus augustifolius, Nich. 



affinis, Nich. Diplograptus serra, Brongn. 



To these I have myself added 



Diplograptus tricornis, Carr. Azygograptus coelebs, Lapw. 



and species of Climacograptus. 



Scandinavia. — The Lower Ordovician rocks of Sweden 

 which correspond to our British Arenig are the so-called 

 Longer- GraptoJite- or PhyUograptus- Schists that underlie the 

 well-known Orthoceras-Limestone. Their included Rhabdo- 

 phora have recently been carefully worked out by Mr. Lin- 

 narsson ; but the majority of the forms he has discovered are 

 as yet undescribed. In the various collections from these 

 beds which I have up to this date had an opportunity of ex- 

 amining I have recognized § : — 



Tetragraptus bryonoides, Hall. Didymograptus constrictus, Hall. 



fruticosus?, Hall. strictulus, Linnrs. 



quadribrachiatus, Hall. Pbyllograptus angustifolius, Hall. 



Didymograptus patulus, Hall. Temnograptus multiplex ?, Nich. 



* Salter, Quart. Journ. Geol. Soc. vol. xix. p. 135 &c. 



t Quart. Journ. Greol. Hoc. vol. iv. p. 223. 



X Nicholson, he. cit. supra. 



§ Compare Linnarsson, Geol. Mag., June 187H. 



