LASIOGRAPTUS. 331 



proceed outward, in some cases to a breadth more than twice that between their 

 points of origin. 



Horizon and Localities. — Upper Hartfell Shales (zone of Dicellog. anceps). 



8. Scotland: Ettrick Bridge End, Selkirk; Dobb's Linn (?). 



Associates, etc. — The only three specimens of this species certainly known come 

 from Ettrick Bridge End and belong to the Collection of the Geological Survey of 

 Scotland, but fragments of a somewhat similar meshwork are not uncommon in the 

 zone of Dicellog. anceps at Dobb's Linn, and may belong to the same form. 



Collections. — Geological Survey of Scotland and the Authors. 



Sub-genus Neurograptus, Lapworth. 



1875. Neurograjrfus, Lapworth, Graptolites of the St. David's Area, Quart. Journ. Geol. Soc, vol. 

 xxxi, p. 641. 



Lasiograptus (Neurograptus) fibratus (Lap worth). Plate XXXIV, figs. 5 a — c. 



1876. Betiolites fibratus, Lapworth, Cat. West. Scott. Foss., pi. iii, fig. 62. 



1877. Betiolites fibratus, Lapworth, Grapt. Co. Down, Proc. Belf. Nat. Field Club, p. 136, pi. vi, fig. 28. 



Polypary not exceeding 5 cm. in length, and having an average breadth of 



about 3 mm. (exclusive of the extraneous processes) ; margins sub-parallel for 



the greater part of their length ; proximal end unknown. Thecas ten in 



10 mm., of the type of those of Hallog. mucronatus. Clathria well 



developed; ventral processes stout, fibrous, originating complete marginal 



lacinia ; septal processes branching, scopulate. Test continuous, greatly 



attenuated. 



Description. — The test in this species is remarkably thin, and the ribs and 



processes of the clathria relatively stout and stiff, so that at first sight the entire 



polypary and its appendages appear to be reduced to a network of interlacing 



threads, symmetrically arranged about two strong septal strands. The central 



theca-bearing portion of the polypary, as represented by its clathria, is narrow 



and inconspicuous, and must have been almost square in transverse section, for the 



width in the bi-profile and scalariform views is about the same. 



There are two septal strands, the most conspicuous of which is practically 

 straight, and the other undulating or zig-zag. In the bi-profile view, the main 

 filaments of the ventral lacinia proceed from the denticle, at first directly out- 

 wards and almost horizontally, while the descending portion is less graceful and 

 flowing than in most other forms of the Lasiograpti. Instead of the delicate minor 



