124 



BRITISH GRAPTOLITES. 



inclined at 10°, have an average length of 1*5 mm., and are free for two thirds of 

 it. The apertural margins occupy about one half the width of the stipe. 



Affinities. — The polypary of var. radiatus is obviously somewhat closely allied to 

 that of A. divergens, since the secondary branching takes place in close proximity to 

 the sicula ; it only differs from A. divergens in its capacity for branching, which 

 appears to be much less than that of the typical form. 



Horizon and Localities. — Hartfell Shales (zones of Dicranog. Glingani and 

 Pleurog. linearis). 



S. Scotland : Dobb's Linn ; Hartfell Spa ; Castle Hill, Abington ; Cairn Burn. 



Associates, etc — Var. radiatus has been recorded from the zones of Dicranog. 

 Glingani and Pleurog. linearis in the Hartfell Shales of S. Scotland, where it occurs 

 in association with Glimacog. candatus and Leptograptus. Specimens are in the 

 collections of Lapworth, the Woodwardian (Sedgwick) Museum, and the Geological 

 Survey of Scotland. 



Amphigraptus distans, sp. 



Plate XVIII, fig 3. 



Main stipes narrow, straight and rigid, 3 cm. or more in length, diverging at 



an angle of less than 180° from a conspicuous sicula, which frequently gives 



rise to an extra stipe. Secondary branches agreeing with main stipes in 



general characters, but somewhat shorter, given off in pairs or sets of pairs, 



with a distance of at least 5 mm. between each set. Thecal seven in 



10 mm., inclined at about 10°, having an average length of 2*5 mm. and 



free for two thirds of it. Apertural margins submucronate, slightly 



introverted, occupying about one third the total width of the stipe. 



Description. — The main stipes and secondary brandies have an average width 



of "5 mm., but perhaps slightly less at their origin. The length of the main stipes 



was probably not less than 4 cm., while that of the secondary branches seems 



not to have exceeded 3 cm. 



A third stipe, or branch, is developed from the sicula or its neighbourhood, in 

 t lie type specimen, so that the details of the proximal end cannot be made out 

 accurately. The sicula appears to have a length of 1 mm. or more. 



The tliecas are long ; in the figured specimen 

 they are well preserved. 



. \Jjlnitics. — A. distavs is characterised by the 

 distance between the sets of secondary branches ; 

 this distance is far greater than that of any species 

 belonging to this genus hitherto described. It 

 number of its secondary branches, but differs in 

 for instead of being close packed they are spread 



Fin. 1~>. A)tqihiij?m>lux ilixtmis, nov. 





Thocae of one of branches, 

 of PL XVIII, fie 



Enlargement 

 3. 



approaches A. divergens in the 

 their position and arrangement: 



