19G BRITISH GRAPTOLITES. 



length. In other respects this form agrees with the typical species. A membrane 

 frequently surrounds each spine, giving to all an appearance of greater width 

 than they naturally possess. 



Horizon and Localities. — Upper Glenkiln and Lower Hartfell Shales. 



8. Scotia ml: Hartfell; Dobb's Linn; Wanlock Water, etc. Wales : Ty Fry, 

 near Portmadoc. Ireland : Ballygrot. 



Associates, etc. — Var. tridentatus is a somewhat rare fossil in the Glenkiln 

 Shales (zone of Dicellog. patulosus), where it occurs associated with CI. bicornis, 

 CI. peltifer, 01. Scharenbergi. It also occurs in the succeeding Lower Hartfell 

 Shales (zone of CI. Wilsoni), associated with CI. Wilsoni and Dicranog. Nicholsoni. 



Collections. — Lapworth and the Authors. 



Var. peltifer, Lapworth. Plate XXVI, figs. 10 a—c. 



1876. Climacograptus bicornis, var. peltifer, Lapworth, Cat. West Scot. Foss., pi. ii, fig. 53. 



1877. Climacograptus bicornis, var. peltifer, Lapworth, G-rap. Co. Down, Proc. Belfast Nat. Field 

 Club, p. 139, pi. vi, fig. 38 6. 



A common variety of CI. bicornis is one in which the membrane surrounding 

 the basal spines has developed to such an extent as to envelop the entire proximal 

 end of the polypary in a triangular disc. The spines form the proximal termina- 

 tion of the disc, which thence extends upward for a distance of 4 — 5 mm. The 

 thecce agree in most particulars with those of CI. bicornis (though the apertural 

 excavations are somewhat smaller, occupying one-fifth of the breadth of polypary 

 as compared with one-fourth in the typical form) ; the form of the polypary is 

 also similar. 



Horizon and Localities. — Upper Glenkiln Shales (zone of Dicellog. patulosus). 



8. Scotland: Dobb's Linn; Hartfell, etc. Wales: Tiddyndicwm. Ireland: 

 Ballygrot; Coalpit Bay. 



Associates, etc. — Var. peltifer is a fairly abundant fossil in the Moffat country in 

 the highest beds of the Glenkiln Shales immediately below the zone of CI. Wilsoni ; 

 with Dicellog. patulosus in most places marking a clearly recognisable zone. It is 

 commonly associated with ( V. bicornis, CI. Scharenbergi, and CI. (?) perexcavatus. 



Collections. — Lapworth and the Authors ; Fearnsides. 



Climacograptus supernus, sp. now Plate XXVI, figs. 11 a — d. 



Polypary small, 1 — 2 cm. in length, widening somewhat rapidly from about 

 0-5 mm. to a maximum breadth of 1*2 mm., which is thereafter maintained. 

 Sicula about 1 mm. in length; virgella short and robust. Thecas of the 

 general l>i<-<>ruis type, fourteen to twelve in 10 mm. 



