Vol. 67.] SALOPIAN ROCKS OF CAUTLEY AND RAVENSTONEDALE. 219 



Cyrtograptus-rigidus Zone (C 3 ). — At the bend of the 



stream the lithological character of the rock changes once more to 

 blue-grey handed flags, much affected by cleavage. Along one 

 bedding-plane Monograptus flexilis is abundant, and it is the only 

 fossil that is easily recognizable. As Ave have found throughout 

 the Cautley area that M. flexilis is common only in the C.-rigidus 

 Zone, it may be taken as an index of that zone. 



A characteristic feature of this zone is the introduction of 

 secondary calcite along the joints and bedding-planes of the rock. 



Cyrtograptus-lundgreni Zone (C ( ). — 100 yards down stream 

 the beds dip 20 c north of north-west at 24°, and maintain their 

 dark coloration and cleaved character. They yield many specimens 

 of Monograptus vomerinus.. Some 30 yards from the upper field- 

 wall, however, the beds change ; they become tougher, and weather 

 to a light brown. M.flemingii var. c and M. dubius were found 

 here. The presence of the former fossil and lithological change in 

 the rocks indicate the C.-lundgreni Zone. 



(ii) Middle Gill. 



Oyrtograptus-murchisoni Zone (CJ. — The felsite-dyke of 

 the old road has baked the Murclvisoni Beds of Middle Gill ; but 

 just below the road a small exposure yields good specimens of 

 C. murchisoni, Monograptus priodon, M. vomerinus, and Retiolites 

 geinitzianus. 



The zone extends down the gill for a distance of about GO yards, 

 and other small exposures indicate that Cardiola and lietiolites 

 geinitzianus are abundant in the higher parts of the zone. 



Monograptus-riccartonensis Zone (C.,). — The passage into 

 this zone is marked by a complete change in the fauna. The 

 name-fossil becomes very abundant]; indeed, slabs of rock are often 

 covered by it, to the exclusion of an)* other. The fossils are, on 

 the whole, badly preserved, as the result of cleavage. A list of the 

 forms found is enumerated in Table I (p. 222). The beds dip 

 at 35° north-westwards. 



Cyrtograptus-rigidus Zone (C. t ). — This zone is well exposed 

 on the right bank of the gill, and extends down stream for (50 yards 

 below the little waterfall. 



The rocks dip at 34° north-north-westwards ; they are highly 

 cleaved, and contain abundant cubes of pyritc, which cause them to 

 weather to a bright orange colour. The higher part of the zone is 

 characterized by the blackness of the fresh rock, and by the abundanl 

 development of secondary calcite. Monograptus flexilis is crowded 

 along definite bands in association with C. rigidus, M. vomerinus, 

 M. hisingeri, 31. dubius, and M. flemingii var. c) ; this last fossil 

 becomes more abundant in the highest part of the zone. 



