390 HONE YM AN ON NOVA SCOTIAN GEaLOGYr 



8, — Felspathic ashy conglomerate. 



4,— Slate. 



5, — Felspar porphyry. 



6, — Blue slate. 



7, — Felspathic trap. 



8, — Blue slaty beds. 



" In places the trap No. 7 is slightly hornblendic, and although 

 probably intruded between the beds it may possibly be a regularly 

 interhedded lava flow, ''^ page 96. In explanations on Plate 28, 

 Section No. 3, the syenite, porphyries and greenstone are referred 

 to the Lower Silurian, 



The adding of a new Fauna ta the Silurians of Nova Scotia 

 seems to be a fitting time for making a few observations on the 

 Fauna already known. 



By common consent the fauna of Arisaig is regarded as typical 

 of the Middle and Upper Silurian of Nova Scotia. All however 

 are not agreed on the points of range and relationship, 



"With the aid and counsel of J. W. Salter, Esq., late Palaeon- 

 tologist of H. M. Survey of Great Britain, I made a subdivision of 

 the Arisaig Series in 1863 — Vide Paper by the Author " On the 

 Geology of Arisaig." Geological Journal, 1863, 



The division then made was alphabetical and British as follows : 



A. Mayhill Sandstone — Salter. 



B. B'. . r Lower Ludlow. 



C .... Aymestry Limestones — Salter. 



D . . , Ludlow Tilestone — Salter. 



After the lapse of 10 years and a great amount of labour and 

 research, I consider that the alphabetical division is the only unobjec- 

 tionable one that has been proposed, and that the only modification 

 of the British division required is the omission of the "Lower 

 Ludlow," which was not suggested by Mr. Salter. Previous to Mr. 

 Salter's examination and correlation, I had correlated D. with the 

 Upper Ludlow of Wales, and Dr. Dawson had at the same time cor- 

 related C. and D. with the Lower Helderberg, U. S., and B'. with 

 the Clinton, U. S. D. and C. are farther distinguished by Dr. 

 Dawson, Upper Arisaig, and B'. Lower Arisaig. Extensive obser- 

 vation has proved that Mr. Salter was correct in giving the Arisaig 

 Series a greater range in time than that given by Dr. Dawson. 



