NEMAGBAPTUS. 129 



Linn; Kelphope Burn; Papana Water; Horten Gill ; Duntercleucli ; Black Linn, 

 etc. Ireland: Ballygrot; Craigavad; Tramore Bridge. 



Associates, etc. — Nemag. gracilis is one of the commonest fossils wherever 

 the Graptolitic facies of the Upper Llandeilo rocks is developed; throughout 

 S. Scotland it occurs in abundance where the central members of the Glen kiln 

 beds occur- It is commonly associated with Didymog. swperstes, Dicellog. sextans, 

 Dicranog. zig-zag, D. tardiusculus, l>. ramosus, Leptog. latus, N. explanatus, and var. 

 pertenuis, N. gracilis, var. surcularis, Diplog. Whitfieldi and other forms. Excellent 

 specimens are in the collections of the Geological Survey of Scotland and the 

 private collections of Lapworth and the Authors. 



Var. surcularis (Hall). Plate XIX, figs. 2 a— d. 



1868. Coenograptus surcularis, Hall, 20th Ami. Report on State Cabinet, p. 171', figs. 13 — 16. 



1876. Coenograptus surcularis, Lapworth, Cat. West. Scot. Foss., pi. iii, fig. 64. 



1877. Coenograptus surcularis, Lapworth, Proe. Belfast Nat. Field Club, p. 143, pi. vii, fig. 12. 



Description. — -In addition to Nemag. gracilis, there occurs associated with it 

 another somewhat closely allied form in which the flexed main stipes, instead of 

 growing one upward and one downward, are both directed upward, and are curved 

 in such a manner that they tend to cross each other at some point along their 

 length. These main stipes have a length of 1 — 2 cm., do not exceed "5 mm. in 

 width, and their direction of growth is extremely characteristic. The secondary 

 branches are short, being about 7'o mm. in length, and their width is also uniformly 

 "5 mm.; they are commonly few in number (about four on each stipe), are only 

 slightly curved, and are situated near the sicula. The average distance between 

 the secondary branches is 1'5 mm., and each branch appears to originate opposite 

 the aperture of a theca on the main stipe. 



The sicula is conspicuous; it has a length of 



Pig. 77 a. — Nemagraptus gracilis, var. i L i i ii c . I i 



surcularis (Hall). about 1 mm., and the nenia can frequently be 



detected at its apical extremity. In the obverse 

 aspect of the polypary the earliest developed thecae 



are seen to originate approximately midway between 

 the apex and aperture of the sicula, but rather 

 nearer to its aperture; they grow slightly downward 



Proximal end. ^Egargement of part of before curv i ng outward, and the appearance of the 



proximal end is characteristically symmetrical; the 



apertures of th. 1' and th. L 2 are submucronate at their lower extremities, and tin' 



first interthecal walls appear to grow back to the sicula. 



