: 



1:30 BRITISH GRAPTOLITES. 



The thecas are always preserved on the outer 



FlGS " " '' ^wS^HaSr gracUiS ' Var ' side of tlie curve of tllc sti P es ' thc 7 are ratner 

 :^?v. more remote on the main stipes than on the 



secondary branches (seven instead of eight in 

 10 mm.). They are inclined at about 10°, have 

 an average length of 1*5 mm., are six times as 

 long as wide, and overlap one-third of their 

 length. 



Affinities. — Var. surcularis is very closely 



/). Thecae at distal end of main stipe. En- n • -i , \r w 1 i •• i t pp , p i • 



largement of pi. xix, fig. 2 a. allied to iv. gracilis, but it has a different fashion 



c. Thecae of one of the branches. Enlarge- £ ,1 t, i i i tt ii 



ment of Pi. xix, fig. 2 a. °* growth. It was regarded by Hall as a 



young form of N. gracilis, but if so the direction 

 of the stipes must have been modified at a later stage of growth of the species, for 

 no large form preserving the aspect of var. surcularis has as yet been found on 

 either side of the Atlantic, although small forms of the type of N. gracilis are 

 not uncommon. We can only consider that they are the same form if we imagine 

 that in the later stages of growth one branch underwent torsion. There appears 

 to be a certain amount of evidence for this view, but it is too small to justify the 

 inclusion of the two under one name. 



Horizon and Localities. — Upper Llandeilo (Grlenkiln). 



8. Scotland : Cairn Hill ; Grlenkiln Burn ; Berrybush ; Rein Gill ; Gair Gill ; 

 Riddenlees ; Papana Water ; Black Linn ; Dibbin Lane, etc. N. Ireland : Ballygrot. 

 Associates, etc. — Var. surcularis is a comparatively common form in the Glen- 

 kiln Shales of S. Scotland, where it occurs associated with Didymog. superstes, 

 Nemag. gracilis, Nemag. explanatus, Dicellog. sextans, and Diplograptus sp. The best 

 specimens at present known are in Lapworth's collection and in that of the 

 Geological Survey of Scotland. 





Var. remotus, var. nov. Plate XIX, figs. 3 a — h. 



Description. — A second variety of N. gracilis in which the branching takes place 

 entirely at the distal extremities of the main stipes is also fairly abundant in the 

 Glenkiln Shales of S. Scotland. This is now described as var. remotus. 



The main stipes in general show the sigmoid curvature characteristic of the 

 typical species and have a length of 2 cm. or more; they are, however, narrower, 

 never exceeding -'o mm. in width. From the outer side of the curve of each main 

 stipe, and near their distal extremities, three or four (possibly more) short 

 secondary branches are given off, and the curvature of these is similar in direction 

 to that of the main stipe from which they arise. The first is developed at a 

 distance of not less than I mm. from the sicula, and the subsequent ones are 

 commonly 2 mm. apart. 



