62 BRITISH GRAPTOLITES. 



1874. Diclymograpiiis (?) fruticosvs, Etheridge, jun., Anu. Mag. Nat. Hist., ser. 4, vol. xi, p. 1. 

 1877. GraptoUtlms {Bidymograj^sus) fruticosns, M'Coy, Prodromus Pal. Victoria, p. 13, pi. i, 

 figs. 9—14. 



Main stipes from 1"5 to 2*5 cm. in length, directed more or less vertically 



downward for greater part of their length, bnt diverging towards their 



distal extremity ; increasing in width gradually and persistently up to a 



maximum of 2 mm. Sicula conspicuous. Thecae seven in 10 mm., inclined 



30° — 35°, two or three times as long as wide, free for one third their length. 



Apertural margins normal, concave, mucronate. 



Description. — The persistent increase in width of the stipes is extremely 



characteristic of the species ; the width opposite the aperture of theca V is only 



1 mm., but it increases steadily thereafter up to a maximum of 2 mm. 



The sicula measures 2 mm., and the first theca 



Fig. 37. — Tctragraptws fruticosus, Hall. / i i\ • • n • 



(th. 1 ) originates near the apex. The dichotomous 

 division of the stipes of the first order appears to 

 take place after the development of two thec£e on 

 each side of the sicula. 



Hall gives the length of the sicula as 12' 7 mm. 

 ("I inch), but it is clear from his figures that this 

 measurement included a considerable portion of the 

 Proximal end, obverse view. Enlarge- nema or virgula : the truB sicula, SO far as Ave have 



ment of PI. VI, fig. 2 6. fa ' 



seen, never exceeds 2 mm. m length. 



The thecje are comparatively remote, and average about seven in 10 mm. in the 

 mature parts of the stipes. This inclination increases slightly with age, those 

 thecae nearest the sicula being inclined at about 30°, while those in the more distal 

 parts have an inclination of about 35°. They are about twice as long as wide 

 near the sicula, but about three times as long in the fully developed parts 

 of the stipe ; the overlap increases from mere contact to a maximum of two 

 thirds the length of the thecse. The aperture is concave and mucronate when 

 well preserved, but slight distortions cause it to appear straight and devoid of any 

 mucro. 



AJjinities. — T. fruticosii.s resembles T. pendens in its general form, but may 

 readily be distinguished from it l)y its greater si/e, the persistent increase in width 

 of the stipes, the number of tliecai in a given unit of length, and their degree of 

 inclination. 



Horizon and Localities. — Arenig. 



S.Scotland: Bennane Head, Ballantrae. Lake District : Raven Grill. 



Associates, etc. — The true T. fruticosns has hitherto been recorded only from the 

 Arenig rocks of the Girvan district (Ballantrae), S. Scotland, where it has been 

 foinid by Jia])\voi'th and the ofiicers of II. M. Geological Sui'vey, in whose 

 collections the specimens are preserved. At Ballantrae it occurs associated with 



