DEVONIAN OF NOVA SCOTIA. 



499 



iron, with dark coloured coarse slates, dipping S. 30° E. at a very 

 higli angle. The iron ore is from 3 to 4^ feet in thickness. The 

 fossils of the ironstone and the accompanying beds, as far as they can 

 be identified, are Spivifer arenosus, Strophodonta magnifica^ Atrypa 

 unguiformis, Strophomena depressa, and species oi Avicida, Belleropho7i, 

 Favosiies, and Zaphrentis, etc. These Professor Hall compares with the 

 fauna of the Oriskany sandstone ; and they seem to give indubitable 

 testimony that the Nictaux iron ore is of Lower Devonian age. The 

 most abundant fossil is a Spirifer as yet not identified with any de- 

 scribed species, but eminently characteristic of the Nictaux deposits. 

 It is usually seen only in the state of casts, and often also strangely 

 distorted by the slaty structure of the beds. The specimens least 

 distorted may be described as follows : — General form, semi-circular 

 tending to semi-oval, convexity modei'ate ; hinge-line about equal to 

 width of shell ; a rounded mesial sinus and elevation Avith about ten 

 sub-angular plications on each side ; a few sharp growth ridges at the 

 margin of the larger valves. Average diameter about one inch ; 

 mesial sinus equal in width to about three plications. I shall call this 

 species, in the meantime, S. Nictavensls. 



I figure two distorted specimens (Fig. 176), to show the i-emarkable 

 differences of form produced in this way. The original form is inter- 

 mediate. 



Fig. 17G. — Sjjirifer Nictavensis. 



(a) Shortened, and (h) lengthened, by distortion, in the direction of the arrow. 



To the southward of the ore, the country exhibits a succession of 

 ridges of slate holding similar fossils, and probably representing a 

 thick series of Devonian beds, though it is quite possible that some of 

 them may be repeated by hiults or folds. Farther to tlic south these 

 slates are associated with bands of crystalline greenstone and quartz 

 rock, and are then interrupted by a great mass of white granite, which 

 extends far into the interior and separates these beds from the similar, 

 but non-fossiliferous, rocks on the inner side of the metamorphic band 

 of the Atlantic coast. Tlie Devonian beds ajipear to dip into the 

 granite, which is intrusive, and alters the slates near the junction into 

 gneissoid rock holding garnets. The granite sends veins into the 

 slates, and near the junction contains numerous angular fragments of 

 altered slate. 



