324 DR. A. M. DAVIES AND ME. J. PRINGLE ON [June 1913, 



(of which the depth-record is lost, hut it should prohahly be about 

 :900 feet) it is associated with a divergence of the laminae of the 

 shale which results in a false appearance of overthrust. 



Occasionally well-marked joints are seen to cross the cores. 

 Where the shales are vertical (1180 to 1220 feet) there are two 

 main joints, at right angles to the bedding and to one another, 

 and running the one almost vertically and the other horizontally ; 

 while a third, less perfect joint, runs at an angle of about 45° 

 both to the bedding and to the horizontal joint. Where the beds 

 :are inclined, the main joints are at right angles (or nearly so) to 

 the bedding, but not one to the other ; and they are oblique to the 

 direction of dip, the angle which they make with it varying in 

 different cases from 25° to 60°. 



After making allowance for the dip, the true thickness of these 

 •shales between the base of the Lias and as far as the Eastern 

 Boring penetrated them, is about 480 feet. The dip varied from 

 40° up to 90°, and there were occasional kinks in the bedding, as 

 for instance at 845 feet, where the general dip was 40°, but it was 

 bent up to 80° about the middle of the core. An effort was made 

 by Mr. Hiorns to ascertain the direction of dip, but the preliminary 

 experiments were so unsuccessful that the attempt was abandoned. 



The following fossils were found : — 



■ Clonograptus tenellus var. callavci 



(Lap worth) at the depths of 496, 

 498, 517, 530, 555, 568, 600, 

 630, and 635 feet. 



■ Clonograptus (?) at 490, 830-850, 



and 1160 feet. 

 Bryograptus (?) at 600 feet. 

 Obolella(?) aff. salteri Holl. (see 



p. 303), at the depths of 498, 



555, 558, 609, 740, and 790 feet 

 (at the last two levels, fragments 

 only). 



Worm-castings, at 960 feet. 



Black, probably carbonaceous 

 patches (remains of alga??) 

 frequently occur. 



Clonograptus tenellus var. callavei (Lapworth) is known from the 

 Shineton Shales of Mary Dingle (Shropshire), and from Zone 2 

 {Bryograptus Zone) of the Geratopyge Beds of Scandinavia. 1 The 

 Calvert specimens at the higher levels are well-preserved and quite 

 characteristic, and an exceedingly fine specimen is in the possession 

 of the Museum of Practical Geology (26239). Mrs. Shakespear 

 writes of them : — 



' The rock is so similar to that typical of the Tremadoc in Shropshire that 

 it is difficult to believe that the specimens do not come from Mary Dingle.' 2 



The presence of Clonograptus leaves no room for doubt that the 

 shales belong to the Lower Tremadoc Series. 



The nearest localities where rocks of the same age are known 



1 J. C. Moberg k O. O. Segerberg, ' Bidrag till Kannedomen om Ceratopyge- 

 Eegionen ' Medell. fran Lunds Geol. Faltklub, ser. B, No. 2 (1906). 



2 Bryograptus is very doubtfully represented by two fragments showing the 

 sicula. Mrs. Shakespear writes: 'I am inclined to think that they are only 

 the proximal end of a Clonograptus, so preserved that the stipes are pendent 

 rather than spread out horizontally. This appearance is not uncommon, and 

 the small fragment shows thecse of precisely the same form as those of 



■ Clonograptus? 



