W. H. Twenhofel — Silurian Section at Arisaig. 151 



mouth of Arisaig brook, but by faulting it is brought to view 

 in the mouth of the brook. Strike 1ST. 86° W. ; clip 16° W. 



Thickness 23 feet. 



This zone appears to coincide with the base of Honey- 

 man's Division B' and the Upper Clinton of Fletcher's section. 

 Fossils: Monograptus 'priodon chapma.nensis, Dalmanella ele- 

 gantula, Anabaia depressa, Cor indites distans, and Dalman- 

 ites sp. 



7. Green arenaceous micaceous shales and fine-grained sand- 

 stones in beds from one to six inches thick. Much fractured. 

 Attitude almost horizontal. Strike N. 20-90° W. ; dip 0-2° W. 



Thickness 30 feet. 



Fossils fairly abundant : Monograptus clintonensis, Orbicu- 

 loidea tenuilamellata, Dalmanella elegantula, Chonetes 

 tenuistriatus, Camarotoechia near equiradiata, Anabaia anti- 

 costiana, Anoplotkeca hemispherica (rare), Schuchertella sp., 

 Avicula emacerata, and fragments of Eurypterus. 



8. Green shales and thin lenticular tine-grained sandstones. 

 Strata in a small synclinal fold. 



Estimated thickness _ 30 feet. 



Fossils very common, especially graptolites : Monograptus clin- 

 tonensis, M. priodon chapmanensis, Retiolites geinitzianus 

 venosus, Orbicidoidea tenuilamellata, Leptmna rhomboidalis 

 (first appearance), Chonetes tenicistriatus, Camarotoechia near 

 equiradiata, Anoplotheca hemispherica (small and rare), Cor- 

 nulites distans, Avicula cf. rhomboidea, Pterinea honeymani, 

 Modiolopsis (?) cf. primigenia, Dalmanites sp. and fragments 

 of Eurypterus. 



9. Light-green, more or less arenaceous shales with numerous 

 lenticular fine-grained sandstones. A shale layer three feet 

 thick full of Lepkena rhomboidalis occurs. The beds are 

 much disturbed and thickness is uncertain. 



Estimated thickness 66 feet. 



Monograptus clintonensis, Chonetes tenuistriatus, Cama- 

 rotoechia cf. obtusiplicata, Rhynchonella cf. robusta, Anoplo- 

 theea hemispherica (rare), Serptdites cf. dissolutus, Cormdites 

 distans, Avicula rhomboidea, Modiolopsis (?) cf. primigenia, 

 and Eurypterus fragments. 



10. Light-green, soft, somewhat papery shales weathering a 

 dirty greenish-yellow and many thin lenticular fine-grained 

 sandstones. This zone begins at a small promontory forming 

 the west end of a synclinal fold which is believed to be the 

 disturbance of zone 18 of Fletcher's section and ends at a fault 

 abont forty yards east of the mouth of Smith's brook. This 

 appears to be the fault described by Fletcher (1886 : 39P) and 



