286 MISS G. L. ELLES AND MISS E. M. K. WOOD ON THE [May 1 896, 



Monograptus turriculatus ; but the fauna, on the whole, shows 

 affinities with the underlying and overlying beds, and we therefore 

 consider that it is of the nature of a passage-bed. We do not know 

 its exact equivalent in other areas. 



The main mass of the Tarannon Shales may be correlated with 

 the lower of the two groups into which Prof. Lapworth (Ann. 

 & Mag. Nat. Hist. ser. 5, vols. v. & vi. 1880) has divided the Gala 

 rocks of the Southern Uplands of Scotland — that is, the zone of 

 Monograptus eociguus. 



It does not seem possible to recognize here the two sub-zones 

 denned by Messrs. Marr and Nicholson (Quart. Journ. Geol. Soc. 

 vol. xliv. 1888, p. 654) in the Lake District. There they found 

 (1) zone of Monograptus turriculatus (Barr.) and (2) zone of 

 M. crispus (Lapw.). In our beds M. turriculatus and M. exiguus 

 range together throughout, but it is noticeable that the genus Retio- 

 lites is confined to the uppermost members of the series. 



The following table shows the relation of the Tarannon Shales of 

 Conway to beds of similar age in the Lake District and Southern 

 Scotland : — 



Conway. 



Lake District. 



South Scotland. 



Tarannon Shales. 



Browgill Shales. 



Lower Gala. 



* Monograptus Becki (Barr.) 



brou ghionensis (Nich.) 



* crispus (Lapw.) 



* 

 * 



* 



* 



* 

 * 



* 



* 

 * 

 * 



* 

 •* 



* 



* 

 * 

 * 



* 



concinnus (Lapw. ) 



* exiguus (Nich.) 



Flemingii (Salt.) 



galaensis (Lapw.) 



Hisingeri,Ya,r.niidus(La,ipw.) 



priodon (Bronn) 



* pandus (Lapw.) , 



runcinatus, var. (Lapw.) ... 



* Cyrtograptus spiralis (Gein.) ... 



Petalograptus ovatus (His.) 



palmeus (Barr.) 



Diplograptus tamariscus (Nich.) 

 * Eetiolites Geinitzianus (Barr.) . . . 

 * obesus (Lapw.) 





It is interesting to note that several of the graptolites found in 

 the Tarannon Shales of Conway seem to be identical with many 

 Swedish forms of the same age. 



3. The Wenlock Shales. 



The correlation of these beds is matter of no difficulty ; they seem 

 to be the equivalents of the Pen-y-glog Slates of the Dee Valley 



