338 BRITISH GRAPTOLITES. 



Horizon and Localities. — Grala-T'arannon and Lower Wonlock Shales, Riccarton 

 Beds. 



8. Scotland : Grieston Quarry, Innerleithen ; Kirkcudbright Bay ; Falbogue 

 Bay, W. side Meikle Ross; Nether Stennis Water; Bsk Reservoir, Pentland 

 Hills. JV. Wales: Conway River, W. side ; Large Quarry Pen-y-glog, Dee Valley. 

 G. Wales : Pencerrig, near Builth ; Tarannon River ; Afon Iaen, near Llanbrynmair ; 

 Plas bach, near Llanbrynmair, etc. Lake District : Pull Beck ; Browgill ; Swindale; 

 Stockdale, etc. 



Associates, etc. — Qladiog. Geinitzianus is a common fossil in the Lower Wenlock 

 Shales, especially in the zone of Gyrtog. Murchisoni, where it occurs associated with 

 Gyrtog. Murchisoni, Monog. priodon, Monog. vomerinus, and other forms. It is also 

 found occasionally in the Tarannon Shales and their equivalents, occurring in 

 the zones of Monog. crenalatus, Monog. griestonensis, and Monog. crispus, associated 

 with the zone fossils. 



Collections. — Geological Survey of Scotland, British Museum (Natural History), 

 Sedgwick Museum, Lapworth, and the Authors, etc. 



Var. angustidens, nov. Plate XXXIV, tigs. 9 a — c. 



In addition to the typical form of Qladiog. Geinitzianus, there occurs a closely 

 allied form which differs conspicuously in being more uniformly narrow throughout 

 its length ; this appears to be worthy of varietal distinction. 



In this variety, which commonly reaches a length of 5 cm. or more, the breadth 

 never exceeds 3 mm. ; it is attained gradually from the proximal end, and the 

 margins are conspicuously parallel for the greater part of their extent. 



Horizon and Locality. — Tarannon Shale, Browgill Beds. 



Lal:e District : Swindale. S. Scotland : Falbogue Bay, W. side Meikle Ross, 

 Kirkcudbright Bay. 



Collections. — Sedgwick Museum (Coll. Fearnsides), Geological Survey of 

 Scotland. 



Retiolites (Gladiograptus) perlatus, Nicholson. Plate XXXIV, figs. 10 a—f. 



1868. Retiolites perlatus, Nicholson, Quart. Journ. Gteol. Soc, vol. xxiv, p. 530, pi. xix, figs. 21, 22. 

 L890. Retiolites cfr. perlatus, Tornquist, Acta Univ. Lund., vol. xxvi, p. 11, pi. ii, fig. 26. 



Polypary with a length of 2 5 cm., and an average uniform breadth of 

 5 mm. ; this breadth is attained by rapid widening from the proximal end, 

 and the margins are distally sub-parallel. Thecas sixteen to twelve in 

 10 mm., indistinct; floors of thecae membranous, sometimes marked by 



