140 Silurian and Devonian Rocks 



are extensively distributed througliout the districts now under 

 consideration ; but the only localities in which they have been 

 clearly recognised, are along a line of outcrop on the northern 

 margin of the hilly region westward of New Canaan. The first 

 and most important of these exposures is at 



NiCTAUX. 



At this place, 20 miles westward of New Canaan, the first old 

 rocks that are seen to emerge from beneath the New Red Sand 

 stone of the low country, are fine-grained slates, which I believe 

 to be a continuation of the Dictyonema slates of Beech Hill. 

 Their strike is N. 30 to 60 E., and their dip to the S. E. at an 

 anMe of 72^. Interstratified with these are hard and coarse 

 beds, some of them having a trappean aspect. In following these 

 rocks to the S. E , or in ascending order, they assume the aspect 

 of the New Canaan beds ; but I could find no fossils except in 

 loose pieces of coarse limestone, and these have the aspect 

 rather of the Arisaig series than of that of New Canaan. 

 In these, and in some specimens recently obtained by Mr. Hart, 

 I observe Orthoceras elegantulmn, Bucania trilohita, Cornulites 

 Jiexuosus, Spirifer rugcecosta f and apparently CJionetes NbvaSco- 

 tica^ with a large Orthoceras^ and several other shells not as yet 

 seen elsewhere. These fossils appear to indicate that there is in 

 this region a continuance of some of the upper Arisaig species 

 nearly to the base of the Devonian rocks next to be noticed. 



After a space of nearly a mile, which may represent a great 

 thickness of unseen beds, we reach a band of highly fossiliferous 

 peroxide of iron, with dark coloured coarse slates, dipping S. 30° E. 

 at a very high angle. The iron ore is from 3 to 4j feet in thick- 

 ness and resembles that of the East River of Pictou, except in 

 containing less silicious matter. The fossils of this ironstone and 

 the accompanying beds, as far as they can be identified, are 

 Spirifer arenosus^ St7'ophodonta magmjim^ Atrypa unguiformis, 



* There is in the iron ore and associated beds another and smaller 

 Spirifer as yet not identified with any described species, but eminently 

 characteristic of the Nictaux deposits. It is usually seen only in the 

 state of casts, and often 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 dia- 

 meter about one inch ; mesial sinus equal in width to about three plica- 

 tions. I shall call this species, in the meantime, S, Nictavensis. 



