324 BRITISH GRAPTOLITBS. 



Sometimes the scopulae present rather the appearance of a bag or disc edged 

 and supported by simple and continuous fibres. In some examples the membrane 

 has disappeared, and all that remains are the supporting fibres. Examples of 

 scopulae-bearing forms are comparatively rare, and few are sufficiently well 

 preserved to be figured. The scopulas themselves are apparently identical with 

 the "reproductive sacs" of Hall ('Canadian Org. Rem.,' dec. 2, 1865, pi. b, 

 figs. 6—11). 



Horizon and Localities. — Llandeilo, Glenkiln Shales. 



8. Scotland : Glenkiln Burn; Polmorlach Burn, Kirkconnel; "Water of Deugh, 

 a few yards below the Moor ; foot of Hawkwood Burn, Wandel Water ; Glentewing 

 Burn ; Back Burn, Crawick Water; Gairy near head of Garryhorn Burn. Wales : 

 Tiddyndicwm. Ireland : Belvoir, Co. Clare. 



Associates, etc. --Var. bimucronatus is a fairly common fossil in certain 

 beds of the Glenkiln Shales of S. Scotland, where it is associated with Nemag. 

 gracilis, Dicellog. sextans, Dlcranog. rectus, Climacog. Scharenbergi, Cryptog. 

 tricornis, etc. 



Collections. — Geological Survey of Scotland, Geological Survey of Ireland, 

 Sedgwick Museum, Lapworth, and the Authors. 



Var. nobilis, nov. Plate XXXIII, figs. 9 a — d. 



A sub-variety of Ilallog. var. bimucronatus is worthy of separate description. 

 It is both longer and broader than var. bimucronatus, and widens so quickly that 



the breadth is a conspicuous feature, even in quite 



Fig. 213 a. — Hallo gravtus binvucr onatus, • 1 • 1 i , ,1 • -i , i • c n 



var. nobilis, nov. y oun g specimens which have not attained their full 



length. In this form, which may be appropriately 





called var. nobilis, the length may reach 7 cm. or 

 more, and the breadth is fully 5 mm. (exclusive of 

 the spinous processes) ; the margins may be parallel 

 for the greater part of their length, or there may 

 be a slight diminution towards the distal extremity 

 a in some of the larger specimens. 



a. Proximal end, reverse aspect. En- ° W ' m S t0 tlleir l ' AV ^ *ize and good state of 



g rg g™ ent of part of P1 - XXXIII > preservation the examples of this variety allow us 



to interpret more perfectly the appearances pre- 

 sented by the spinous processes than in var. bimucronatus proper. The spines are 

 longer and more flexed; their fibrous extremities hang down in graceful curves, 

 sometimes reaching and passing beyond the level of the spines below. Some 

 specimens show a septal strand distinct from the virgular tube, and short 



