DIPLOGRAPTUS. 237 



Var. pauperatus, var. nov. Plate XXIX, figs. 5 a — d. 



Another common variety of Orthog. truncatus is a short and narrow form which 

 is practically confined to the zones of Dicranog. Glingani and Pleurog. linearis, and 

 which has been appropriately termed pauperatus. In this the length is occasionally 

 as much as 4 — 6 cm., but smaller forms are far commoner, and no specimens 

 exceed 2 mm. in breadth in Lapworth's Collection. This width is attained within 

 5 mm. of the proximal end, so that the polypary is characteristically narrow. 

 The thecse number fourteen to twelve in 10 mm., and they never overlap for more 

 than half their length. 



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

 Pleurog. linearis). 



8. Scotland : Dobb's Linn ; Hartfell, etc. Ireland : Ballygrot. 



Associates, etc. — Var. pauperatus appears to be especially characteristic of the 

 zone of Dicranog. Glingani, though it also ranges up into the zone of PI. linearis. 

 It is commonly associated with Diplog. calcaratus var. basilicus and crowds of 

 Gorynoides. 



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



Var. socialis, Lapworth. Plate XXIX, figs. 7 a — e. 



1880. Diplograpius socialis, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 166, pi. iv, figs. 13 a — e. 



A still smaller variety of Orthog. truncatus, which has all the aspects of a 

 starved or dwarfed form, is especially characteristic of the zone of Dicellog. 

 complanatus in the Upper Hartfell Shales. 



The polypary never exceeds 1"5 cm. in length, and forms of less than 1 cm. 

 are of commoner occurrence, while the average breadth is only 1*5 mm. The 

 Figs. 157 a and b—Orihograptus trim- thec83 number fourteen to twelve in 10 mm. ; they 



caius, var. socialis, Lapw. ,.,.. . „. . „ . K _ 



have a general inclination in profile view or 4o , 



„, h' have a length of about 1*5 mm., and overlap one 



>, // C\\ J i-l • -l j 1 _lf j-l '_■ .__i.__j_ . .1. ._■_ i 1 



' / ; x <2s third to one half their extent ; their apertural 



margins are like those of the typical form but 

 somewhat less everted in profile view. 

 a i, The sicula is long (2 mm.), and is free on one side 



a. Proximal end, reverse aspect, but f or a small fraction of its length; th. I 1 originates 



upper part of specimen removed so ° 



as to show the interior of the obverse near the aperture and grows at once upward and 



side and hence the sicula. Coalpit , . . „„ . ..... 



Bay, Co. Down; Birkhill Shales outward, giving oft a Spilie SOllie little distance 

 (zone of Diccllog. complanatus). . ,i-io ,i -tit i 



Coil. Lapworth. below the aperture ; th. i~ crosses the sicula obliquely 



b. Similar part of the obverse side of 1 pp . i -, • , -, . , 



another specimen on same slab. and gives oft a spine where direct upward growth 



