LASIOGRAPTUS. 



325 



Figs. 213 b and c. — Hallogragtus bimucronatus, var. nobilis, nov. 



- * J 



1 





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b. Distal end, showing straight virgular tube and curved septal strand 



throwing off processes. Enlargement of part of PI. XXXIII, fig. 9 a. 



c. Distal end, showing paired thecal spines, and also thickened septal strand 



giving off spurs. Enlargement of part of specimen on same slab as 

 Fie. 213 b. 



processes or, more rarely, 

 scopulse are given off from 

 this strand well beyond 

 the distal extremity of the 

 polypary (Fig. 213 6). All 

 the polyparies of this sub- 

 variety preserved in a sub- 

 scalariform or scalariform 

 view show scopulae, and 

 at the same time parts of 

 the thecal spines. 



Horizon and Localities. 

 — Glenkiln Shales. 



8. Scotland : Burn 

 W.N.W. of Low Glenling, 

 7 miles W. by S. of Wig- 

 town ; Pulharrow Burn, 

 Carsphairn. 



Collection. — Geological 

 Survey of Scotland. 



Sub-genus Thysanograptus, nov. 



Those forms of Lasiograpti which possess thecas of the typical Amplexograptus 

 type and are provided with a marginal meshwork or lacinia of delicate connected 

 filaments were alone originally included by Lapworth in his genus Lasiograptus. 

 As this genus is here extended to embrace in addition other closely related species, 

 we suggest the name Thysanograptus as a sub-generic title for the forms typified 

 by Lasiograptus Harknessi and its variety costatus, to which the generic title was 

 first applied. 



Lasiograptus (Thysanograptus) Harknessi (Nicholson). Plate XXXIV, figs. 1 a — d. 



1867. Diployrapsus Harknessi, Nicholson, Geol. Mag., vol. iv, p. 262, pi. xi, fig. 6. 



Polypary small, rarely exceeding 8 mm. in length, with an average uniform 

 breadth of about 2 mm. exclusive of the external processes. Thecge alternate, 

 twelve in 10mm., of the type of Amplexograptus. Lacinia ventral, delicate; 

 occupying a space on both sides of the polypary equal to about half the 



