MONOGRAPH'S. 



4 1-3 



Figs. 304 d, e.—Mowgraptus Sedg- geen \ VOlU( l scem to 1)0 largely a matter of prrsor- 



wickii (Port lock). ° • / ' 



vation, this specific or varietal separation of the 

 '**^> Lake District forms does not appear to us to be 



justifiable, and we have therefore united all under 

 Portlock's original designation. 



Affinities, — -The proximal end of Monog. Sedg- 

 wickii, closely resembles that of M. Haiti and .1/. 

 widulaius. From M. Halli this species, generally 

 speaking, may be distinguished by (1) its less rapid 

 increase in breadth, (2) the more flexed character 

 of distal fragments, (3) the lesser amount of overlap 

 of the theca?, and (-4) the greater retroversion of 

 the apertural regions. In M. undulatus the theca 1 

 are never spined, and there is no change either in 

 the character of the thecse as in M. Sedgwickii, the 

 proximal type persisting throughout, or in the 

 breadth of the polypary, which remains slender 

 from end to end. 



Horizon and Localities. — Upper Llandovery (zone 

 of M. Sedgivickii). 



S. Scotland : Dobb's Linn ; Belcraig Burn ; 

 Sundhope-on- Yarrow ; Selcoth Burn ; Lockerbie ; Plewlands Burn, Raehills. 

 Ireland: Limehill, co. Tyrone; Side Valley, Little River, Pomeroy. Lake District: 

 Skelgill ; Tributary, Haw Gill ; Torver Beck ; Long Sleddale ; Browgill. Wales : 

 Tributary of River Twymyn, Llanbrynmair ; Morben Quarry, Machynlleth; Nant 

 Fuches-wen, Pont Erwyd ; Rheidol Gorge, Pont Erwyd ; Parys Mountain, 

 Anglesea. 



Associates, etc. — Monog. Sedgwickii is usually an abundant fossil wherever the 

 rocks of the Upper Llandovery afford graptolites. It is commonly associated 

 with Modoc/, tenuis, M. Clingani, M. regularis, Climacog. scalaris, and Glyptog. 

 served us var. barbatus. 



Collections. — Geological Survey of England and Wales, and of Scotland, Sedg- 

 wick Museum, Jones, Lapworth, and the Authors. 



d. Mature theca?, compressed, with con- 



spicuous spine. Duffkinnel Burn, 

 Wamphray, S. Scotland ; Upper 

 Birkhill Shales. British Museum 

 (Nat. Hist.) 



e. Part of same specimen, in relief, 



showing that the spines may be 

 completely concealed. 



Monograptus Halli (Barrande). Plate XLIV, fig. 8 a—f. 



1850. Graptolithus Halli, Barrande, Grapt. de Bohi-me, p. 48, pi. ii, figs. 12, 13. 



1876. Monograptus Halli, Lapworth, Geol. Mag. [2], vol. iii, p. 354, pi. xiii, figs. 1 a — d. 



1880. Monograptus crassus, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 155, pi. iv, fig. 8b. 



Polypary long, resembling that of M. Sedgwickii in general form, but straighter 



