W. H. Twenhofel — Silurian Section at Arisaig. 153 



Fletcher (1886 : 3TP), and in part with Division C of Honey- 

 inan (186-1: 333). It consists chiefly of dark splintery arena- 

 ceous shales with a total thickness of one thousand and twenty 

 feet. 



13. More or less thick-bedded greenish-gray to dark-gray 

 rubbly argillaceous limestone and splintery micaceous-arenace- 

 ous shale. The zone is much disturbed and at its base is 

 thrown into a small anticlinal fold of which the eastern limb 

 has been broken off and elevated an unknown distance. Strike 

 N. 56°-72° W. ; dip 32°-37° W. 



Estimated thickness 140 feet. 



If one may judge from Honey man's map (1864: 336), this 

 zone forms the base of his Division C. Fossils abundant: 

 Mariacrinus (?), Dalmanella elegantida, JLeptcma rhomboida- 

 lis, Stropheodonta sj). 1, Camarotwc/iia neglecla, C cf. obtu- 

 siplicata, Atrypa reticularis (first appearance). 



14. Dark-blue to gray micaceous-arenaceous shales with a 

 few flags and thin limestones to a large trap bowlder at foot of 

 cliff. Strike K 76° W. ; dip 32° W." 



Thickness 33 feet. 



Fossils abundant : Dalmanella elegantula, Camarotwcliia neg- 

 lecta, Tentaculites, Homalonotns dawsoni (?). 



15. Greenish-gray interbedded arenaceous-argillaceous lime- 

 stone and shale to McAdam's boat landing. Zone much dis- 

 turbed. Strike N. 64° W. to JST. 57° E. ; clip 42° W. to 39° E. 

 Much of the shore follows line of strike. 



Thickness estimated at 63 feet. 



Pholidojis implicata, Dalmanella elegantida, D. n. sp. very 

 large, like D. edgelliana, Camarotcechia neglecta, Pterinea 

 emacerata,Calymene, Homalonotus dawsoni (?). 



16. Dark-gray shales. Strike ]S T . 64° W. ; dip 33° W. 



Thickness 24 feet. 



Fossils common: Dalmanella elegantida, Camarotwcliia neg- 

 lecta, Tentaculites. 



17. Greenish-gray and dark-gray, crumbling, more or less 

 arenaceous shales. Strike J\ T . 75° "W. ; dip 37° W. 



Thickness 88 feet. 



Fossils scarce : Dalmanella elegantida, Camarotmchia neglecta. 



18. Hard shales, breaking into dagger-like fragments, and 

 knotty calcareous flags with nearly pure limestone lenses. Strike 

 N. 80° W.; dip 40° W. 



Thickness 49 feet. 



Fossils scarce : same as in 16 with Chonetes tenidstriatus. 



Am. Jour. Sci.— Fourth Series, Vol. XXVIII, No. 164.— August, 1909. 

 11 



