252 BRITISH GRAPTOLITES. 



pression of the inner corner of the apertural margin showing through from the 

 under side. 



Affinities. — G. teretiusculus shows many points of resemblance to G. dentatus, 

 but it may be distinguished by its more distant and less introtorted thecas. From 

 G. teretiusculus, var. euglyphus, it differs notably in the characters of the proximal 

 end. 



Horizon and Localities. — Upper Llandeilo ; Dicranograptus Shales. 



Wales: Pencerrig, near Builth ; Gwern-y-fed-fach, near Builth; Newport; 

 Spittal Road Cutting, Pembrokeshire. 



Associates, etc. — Glyptog. teretiusculus occurs in some abundance in the 

 Llandeilo rocks of "Wales ; it is commonly associated with Nemag. pertenuis, 

 Dicellog. sextans, and other forms. 



Remarks. — This species is very like Hall's Diplog. angustifolius, with which 

 it may eventually be shown to be identical, in which case Hall's name will have to 

 be relinquished. 



Collections. — Sedgwick Museum, Lapworth, and the Authors. 



Var. euglyphus, Lapworth. Plate XXXI, figs. 2 a — d. 



1877. Diplograptue dentatus, Lapworth, Grapt. Co. Down, p. 132, pi. vi, fig. 13. 

 1880. Diplograptus (Glyptograptus) euglyphus, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 166, 

 pi. iv, figs. 14 a — e. 



Fig. 172. — Glyvtograptus teretiusculus, 



var. euglyphus, Lapw. 1 1 use nt ns there commonly OCCUl'S 111 S. Scotland a 



J 



In place of the typical form of Glyptog. tere- 

 sculus there commonly occurs in S. Scotland a 

 variety which differs from the type (1) in having a 

 longer and more tapering polypary ; (2) in the 

 absence of lateral spines on the basal thecae ; and (3) 

 in having the thecae more remote in the proximal 

 region. The polypary was parallel-sided for a great 

 length, since fragments 10 cm. long and of uniform 



Proximal end, reverse aspect. Birnock width ai'O kllOWll ; its proximal end, llOWevei', is 

 Water, Alrin<f ton ; (xlenkiln Shales. , . , . , „ 



Coil. Lapworth. pointed rather than square, as m the type form. 



The thecae never exceed eleven to ten in 10 mm. 



Horizon and Localities. — Glenkiln Shales (zone of Nemag. gracilis). 



8. Scotland: Dobb's Linn; Cairn Ryan; Craigmichan Scaurs; Rein Gill; 

 Leadhills ; Glenkiln Burn, etc. 



Associates, etc. — Var. euglyphus is a fairly common fossil in the Glenkiln Shales 

 of S. Scotland, where it occurs associated with Dicellog. sextans, D'uhjmog. 

 superstes, Amplexog. perexcavatus, Nemag. gracilis, and other forms. 



Collcrliuns.— Geological Survey of Scotland, Sedgwick Museum, Lapworth, 

 and the Authors. 



