212 BRITISH GRAPTOLITES. 



in the British Museum (Natural History). The best Irish specimens are in the 

 Collection of the Belfast Naturalists' Field Club, while those from the Lake 

 District were collected by Dr. J. E. Marr, and are now in the Sedgwick Museum. 



Group TV. 



Glimacograpti in which the straight and vertical free edge of the theca is 

 provided with a mesial spine, and the apertural margin tends to be slightly intro- 

 verted. 



Climacograptus innotatus, Nicholson. Plate XXVIT, figs. 10 a — e. 



1809. Climacograptus innotatus, Nicholson, Aim. Mag. Nat. Hist., ser. 4, vol. iv, p. 238, pi. xi, 



figs. 16, 17. 

 1870. Climacograptus innotatus, Nicholson, Ann. Mag. Nat. Hist., ser. 4, vol. vi, p. 384. 



1876. Climarograptus innotatus, Lap worth, Cat. West Scot. Foss., pi. ii, fig. 54. 



1877. Climacograptus innotatus, Lapworth, Q-rap. Co. Down, p. 140, pi. vi, fig. 37. 



I'olypary small, 5 — 6 mm. in length, with a uniform average width of l\ r > mm. 



exclusive of the spines. Sicula 1 mm. in length, virgella short and fine. 



Theca 1 fourteen in 10 mm., short, about 1 mm. in length, in contact only. 



Apertural margins horizontal, opening within wide semicircular excavations, 



which are of the same extent as the free edge of each theca, from the mesial 



angle of which a short and conspicuous spine projects. 

 Description. — The spined nature of the thecae is highly characteristic of this 

 species, as is also its small size and uniformly narrow 



F " ;s W3 ilnotL]'^fci maC09raptWS widtn - Thc * icilla is sma11 ; {t reaches to the level 

 of the aperture of th. I 2 , the initial part of which 

 crosses it obliquely, leaving it free on one side for a 



small fraction of its length. The virgula is often 



slightly prolonged distally. 



Affinities. — Tn the spined nature of the theca 1 



the polypary shows undoubted affinities with the 



a ,, Lasiograpti, but in other respects the characters are 



a. Specimen showing typical form of those of a true Climacograptus, from all species of 



Long Linn, Dobb's Linn; Birkhil] which, however, the presence of the spines is suffi- 

 Shalea (zone of Monog. gregarius) 



Coll. Elles. cient to distinguish it. 



h. P lv preserved lml complete sped- . , . . 7 . . . 



men showing portion of sicula and Horizon <hi<l Localities. — Lower Ibrklnll Shales, 



virgula, On same slab as PI. ,- , < i ; • i, , 1 ■. r 



xxvii, fig. loc zones ol Ueplialog. acummatus, I', vesiculosus, and 71/. 



gregarivs. 



