236 BRITISH GRAPTOLITES. 



etc. N. Ireland: Pomeroy Tirnaskea. N. Wales: Deganwy Quarry; Conway 

 Castle. 



Associates, etc. — Var. abbreviatus is especially characteristic of the highest 

 beds of the Hartfell Shales {Dicellog. anceps zone), where it occurs in great 

 abundance associated with Dicellog. anceps, var. ornatus, CI. supernus, and 

 Eetiolites sp. A few specimens have also been found in the zone of Dicellog. 

 complanatus, associated with the zone fossil, Orthog. truncatus var. socialis, and 

 Climacog. miserabilis. The Birkhill specimens are generally a little smaller than 

 those from the Hartfell Shales. 



Collections. — Lap worth and the Authors. 



Var. intermedius, var. nov. Plate XXIX, figs. 4 a — e. 



Figs. 156 a and b.—Orthograptus trun- Another common variety of 0. truncatus, which 



catus, var. intermedius, nov. ., -, . . .. r> , i t tt j p -n 



is, however, characteristic ot the Lower Hartlell 

 Shales, is here distinguished as var. intermedius. 

 It attains a great length, commonly measuring 

 8 — 13 cm. or more, and has an average breadth not 

 exceeding 2 - 5 mm., which is attained within the 

 first 2 cm., so that the polypary is parallel-sided for 

 the greater portion of its length. 



The theca3 are somewhat intermediate in cha- 



a I) 



racter between those of 0. truncatus and those of 



a. Proximal end, reverse aspect. En- 

 largement of part of pi. xxix, fig. Gh/ptograptus. They measure fourteen to ten in 



4 c. 



6. Distal thecal Enlargement of part 10 mm., and overlap one half their extent; in 



of PI. XXIX, fig. 4 b. _. . r . . ,. , 



common profile view they are inclined at a lower 

 angle with respect to the axis of the polypary, and the apertural margins are 

 less conspicuously everted than in the typical form. 



Horizon and Localities.- — Lower Hartfell Shales (zones of Climacog. Wilsoni 

 and Dicranog. Clingani). Upper Glenkiln Shales (?). 



S. Scotland : Hartfell ; Dobb's Linn, etc. 



Associates, etc. — Var. intermedius is especially characteristic of the zone of 

 CI. Wilsoni, and also occurs in the zone of Dicranog. Clingani; it is very rare in 

 the higher Glenkiln Shales. In the lower zone of the Hartfell Shales it occurs 

 associated with Orthog. calcaratus, var. vulgatus, CI. tridentatus, CI. Scharenbergi, 

 and Dicranog. Nicholsoni, and on the higher, with Dicranog. Clingani, Leptog. 

 flaccidus, Orthog. calcaratus, var. basilicus, and other forms. 



Collections. — Sedgwick Museum, Lapworth, and the Authors. 





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