PLATE XXVIII {continued). 



Figs. 



6 a—d.—Orthograptus Whitfieldi (Hall). (Page 227.) 



6 a. I incomplete, but typical, specimen. Rein Grill, Abington. Glenkiln 



Shales. Geological Survey of Scotland, Edinburgh. 

 I) b. Characteristic specimen, with long virgella. Berry bush Burn, 



St. Mary's Loch. Glenkiln Shales. Geological Survey of 



Scotland, 

 (i c. Broad distal fragment. Belcraig Burn. Glenkiln Shales. 



Geological Survey of Scotland. 

 (i d. Small proximal fragment. Tiddyndicwm, N. Wales. Llandeilo 



Beds. Sedgwick Museum. 



7 a — c- — Orthograptus insectiformis, Nicholson. (Page 228.) 



7 a. Typical, but incomplete, specimen. Dobb's Linn. Birkhill 



Shales (zone of Monog. gregarius). Lapworth's Collection. 

 7 b. Somewhat broader distal fragment. Ibid. 



7 c. Small, incomplete specimen. Ibid. 



8 a — d.—Orthog'raptus vesiculosus, Nicholson. (Page 229.) 



8 a. Typical and complete specimen, "bi-scalariform" view. Coalpit 



Bay, Co. Down. Lower Birkhill Beds. Museum of Natural 

 History Society, Belfast. 



8 b. Small, complete specimen, showing sicula. Dobb's Linn. Birk- 

 hill Shales (zone of Orthog. vesiculosus). Lapworth's Collection. 



8 c. Broad specimen, " bi-scalariform " view, obverse aspect. Ibid. 



8 d. Well-preserved specimen, sub-scalariform view. North end of 



Clanyard Bay, Drummore, Wigtown. Lower Birkhill Shales. 

 Geological Survey of Scotland. 



9 a—c. — Oritwgraptus vesiculosus, var. penna, Hopkinson. (Page 231.) 



9 a. Type specimen, incomplete, figured Hopkinson, ' Geol. Mag.,' 



1872, vol. ix, pi. xii, fig. (>. Frenchland Burn, Moffat. Lower 



Birkhill Shales. Sedgwick Museum. 

 *.> b. Incomplete specimen. Keisley, Westmoreland. Llandovery. 



Fearnsides' Collection. 

 9 c. Complete typical specimen. Frenchland Burn ? Lower Birkhill 



Shales. Geological Survey of Scotland. 



