DEVONIAN OF NOVA SCOTIA. I '.'.I 



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

 high angle. The iron ore is from 3 to l.l Feel in thickness. The 

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

 be identified, are Spirifer arenosus, Strophodonta magnified, Atrypa 

 tmgiuformis, Stropkomena depressa, and species of Avicula, Bellerophon, 

 Favosites, and Zaphroitis, etc. These Professor Hall compares w ith 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 moderate ; hinge-line about equal to 

 width of shell ; a rounded mesial sinus and elevation with 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. Nlctavensis. 



I figure two distorted specimens (Fig. 176), to show the remarkable 

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

 mediate. 



Fig. 176. — Spirifer Nictavemis. 



(a) Shortened, and (6) lengthened, hy 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 faults or folds. Farther to the south tfa 

 slates are associated with bands of crystalline greenstone and quarts 

 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 metamorphie band 

 of the Atlantic coast. The Devonian beds appear 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 

 6lates, and near the junction contains numerous angular fragments of 

 altered slate. 



