186 



BRITISH GRAPTOLITES. 



Var. normalis, Lapworth. Plate XXVI, figs. 2 a — g. 



1877. Climacograptus scalaris var. normalis, Lapwortli, Grrap. Co. Down, Proc. Belfast Nat. Field 

 Club, p. 138, pi. vi, fig. 81. 



110 a, b,c. — Climacograptus scalaris, 

 var. normalis, Lapw. 









Though the typical form of Gl. scalaris (as described by Tullberg from 

 Hisinger's specimens) seems to be found in Britain only in the Upper Birkhill 



Shales and their equivalents, a variety of it, var. 

 normalis, occurs in abundance in the Lower Birkhill 

 Shales, particularly in the Moffat country in the 

 so-called " gingerbread " bed at their base. This 

 variety differs chiefly from the type form in point of 

 size, attaining often a length of about 5 cm., but 

 never exceeding 1*5 mm. in breadth and often 

 barely exceeding 1 mm. The margins of the poly- 

 pary are usually sub-parallel for the greater part 

 of their extent, but some individuals appear to widen 

 more gradually than others. 



Horizon and Localities. — Lower Birkhill Shales 

 and highest Hartfell Shales. 



8. Scotland : Dobb's Linn, Garple Linn, etc. 

 Wales : Rhayader District. Ireland : Donaghadee, 

 Co. Down, etc. 



Associates, etc. — Var. normalis seems to make 

 its first appearance in the Dicellogr. anceps zone, but 

 it occurs most abundantly in the zone of Gephalog. 

 acnminatus, where it is commonly associated with the 

 zone fossil and Gl. rectangularis. Some individuals 

 survive into the overlying zones of Divlog. vesicidosus 

 where they are associated with D. vesicidosus and 

 Coil. Lapworth. various Dimorpliograpti ; and a few continue into the 



zone of Monog. gregarius. It has never been found in the Upper Birkhill Shales. 

 Lapworth and the Authors. 



a. Obverse view. Dobb's Linn, Lower 



Birkhill Shales (zone of Cephalog. 

 acnminatus). Coll. Lapworth. 



b. Eeverse view. Ibid. Coll. H. Lap- 



worth. 



c. Obverse view showing part of sicula. 



Ibid. Coll. Lapworth. 



Fig 



119 d. — Climamgraptiis scalaris, 

 var. normalis, Lapw. 



d. Distal thecae showing their genei - al 

 form. Dobb's Linn, Lower Birkhill 



Shales 



( ■ollections. 



Var. miserabilis, var. nov. Plate XXVI, figs. 3 a — h. 



A form that may be regarded as the forerunner of the scalaris sub-group of 

 Glima,cograj)li makes its appearance in the Dicellograptus complanatus zone. 

 It is a characteristically small, uniformly narrow form, averaging 1 — 2 cm. in 



