112 BRITISH GRAPTOLITES. 



Affinities. — Var. arcuatus is somewhat closely 



Figs. 66 a and 6 — Leptograptus flaccidus, •■,-,•■, 



var. arcuatus, nov. allied to L. capillaris as respects its habit, but the 



stipes are less curved, and the thecas show more 

 *^w I y-^ affinity with those of L. flaccidus. 



^^w| £3 ''' Horizon and Locality. — Lower Hartfell Shales. 



8. Scotland : Hartfell Spa. 



Associates, etc. — Var. arcuatus occurs on slabs in 

 6 the Lower Hartfell Shales in great profusion, to the 



a. Obverse view. Enlargement of part exclusion of all other Graptolite forms. Its aSSO- 



of PI. XV, fig-. 3 a., l 



b. Distal thecal. Enlargement of part ciates are unknown. The best specimens are in 



Lapworth's collection. 



Leptograptus capillaris (Carruthers). Plate XV, figs. 4 a— d. 



1855. Non Nemagrapsus capillaris, Emmons, American Geology, vol. i, p. 109, pi. i, fig. 7. 

 18G8. Cladograpsus capillaris, Carruthers, Geol. Mag., vol. v, p. 130, pi. v, fig. 7. 



1875. Non Nemagraptus capillaris, Hoplunson, Quart. Journ. Geol. Soc., vol. xxxi, pi. xxxiv, 

 figs. 2 a, 2 b. 



1876. Leptograptus capillaris, Lapworth, Cat. West. Scot. Foss., pi. iii, fig. 72. 



Stipes commonly 4 — 8 cm. in length, slender and very much flexed, widening 



from a breadth of about "2 mm. near the sicula to a maximum of "5 mm. in 



the more distal parts of the stipes. Sicula about 17 mm. in length, but 



rarely complete. Thecre eight to ten in 10 mm. on inner or outer side of 



curve, inclined at a very low angle, and free about one-half of their 



length. Apertural margins very narrow, inconspicuous. 



Description. — The stipes are always more or less slender and thread-like; they 



never exceed *5 mm. in width. Their curvature is very pronounced and extremely 



characteristic, each stipe frequently describing the greater part of a circle in the 



course of its growth in an upward or downward direction ; the curved stipes may 



cross each other, or may be coiled upon each other, or upon themselves, so that 



^ m r ± x .„ . ._, , there is great variety in the ultimate form attained, 



Fici.fi/ tt. — LrjilfKjriiiilnsi-itpilhinsti ;irr). ° •> 



the only constant feature being the excessive amount 

 of curvature. 



The sicula is 2 mm. in length and very slender, 

 obverse view. Hartfell Spa, Hartfell but is seldom completely preserved. 



The characters of the thecas are usually hard 

 to determine ; owing to the extensive tenuity of the stipe and its curvature, 

 they are but rarely seen in continuous succession, and their apertures are so 

 minute, except in the case of th. 1' and th. I 2 , that they are generally visible 



