134 BRITISH GRAPTOLITES. 



Var. pertenuis (Lap worth) . Plate XIX, figs. 7 a — /. 



1876. Ccmograptus pertenuis, Lapworth, Cat. West. Scott. Foss., pi. iii, fig. 67. 



1877. Ccenograptus pertenuis, Lapworth, Proc. Belfast Nat. Field Club, p. 143, pi. vii, fig. 13. 

 1899. ? Leptograptus antiquum, T. S. Hall, G-ool. Mag., dec. iv, vol. vi, p. 448, pi. xxii, figs. 5, 6. 



Description. — There occur in association with N. explanatus forms in which the 

 stipes are somewhat more flexed and the thecse slightly more remote ; in addition 

 there seem to be no secondary branches in the same unit of length. No complete 

 specimens are known, so that it is impossible to say with certainty whether there 

 are any secondary branches, but there are none within the same distance of the 

 sicula as there are in N. explanatus. 



The sicula has a length of T2 mm. when complete, but is frequently broken. 



The thecal number six to seven in 10 mm., they 

 Figs. 82 a and b.— Nemagraptus ezpia- are inclined at about 10°, are 2*5 mm. in length, and 



natus, vax. pertenuis (Lsup-w.). _ ° 



free for three quarters of their extent ; they are 

 about six times as long as wide. The apertural 

 margins are concave and introverted. 



Affinities. — Var. pertenuis is obviously most 

 closely allied to N. explanatus, but is distinguished 

 from the typical form by the general absence of 

 1 (ranching and the greater remoteness of the thecaa. 



In the general absence of branching it suggests 



a. Proximal extremity. Enlargement .. . ,, ,, ,- . .. , „ 



of part of pi. xix, fig-. 7 e. a connection with the Leptograph, but on account of 



b. Distal tliccii'. Fiiilartivmi'iit of part ,i p p ,i • n •, 



of pi. xix, fig. 7 a. the fragmentary nature ot the specimens and its 



close relationship with N. explanatus it seems advis- 

 able, for the present at any rate, to retain it with the Nemagrapti. 



Horizon and Localities. — Upper Llandeilo (Glenkiln). 



8. Scotland; Birnock Water; Rein Gill; Glenkiln Burn; Belcraig Burn ; 

 Hack burn ; Crawick Water, head of R. Stinchar; Hawkwood Burn; Gair Gill; 

 Riddenlees; Cowie's Linn; Kelphope Burn; Papana Water; Horten Gill; Dunter- 

 cleuch; Kiln Burn, etc. N. Ireland: Ballygrot. 



Associates, etc. — Var. pertenuis is an abundant form in the Glenkiln Shales 

 of S. Scotland, where it occurs in association with Nemag. gracilis, var. surcularis, 

 Dicellog. sextans, Dicranog. rectus, Dicranog. ramosus, Diplograptus, sp., and other 

 forms. It also occurs with similar associates in N. Ireland. There are good 

 specimens in the collections of the Geological Survey of Scotland, Lapworth, and 

 the Authors. The type specimen is in Lapworth's collection. 



