LEPTOGRAPTUS. 



113 



Lvploijniplus copilluris (Can - ). 



Distill theca 1 . Enlar^'emi'iit of part of 

 PL XV, fig. 4 b. 



merely as slight notches in the wall of the stipe. 

 The apertures of th. I 1 and th. I 2 are, however, 

 conspicuous and mucronate. The mature thecae 

 have a length of about 2 mm. and are in contact 

 for one-half to one-third of their length. 

 Affinities. — L. capillaris may be readily distinguished from all other Leptograpti 

 by the extreme tenuity of its stipes and their pronounced curvature. 

 Horizon and Lucidities. — Lower Hartfell. 



8. Scotland: Hartfell Spa; Ettrick Bridge End; Belcraig Burn. 

 Associates. — L. capillaris is an abundant form in the upper zones of the Lower 

 Hartfell Shales, having a characteristic gregarious habit. It is found most 

 frequently in the zone of Pleurog. linearis, where it occurs associated with L. 

 flaccidus, Diplog. truncatus, var., and other forms. A few specimens have been 

 recorded from rather lower horizons. Good specimens are in the collections of 

 Lapworth and the Geological Survey of Scotland, and the types are in the British 

 Museum. 



Leptograptus validus, Lapworth MS. Plate XVI, figs. 1 a- 



Polypary several centimetres in length ; stipes somewhat rigid or but very 

 slightly flexed, diverging at a wide angle from a conspicuous sicula, 

 wide at origin and increasing gradually to a maximum breadth of about 

 1 mm., which is maintained for the greater part of their length. Thecae ten 

 to eleven in 10 mm., inclined at about 10°, free two-thirds to one-half 

 their length. Apertural margins circular, entire, slightly concave when 

 compressed, nearly perpendicular to the axis of the stipe, and occupying 

 about one-half of its width. 

 Description. — The stipes are typically rigid, but may be slightly flexed; this 

 slight flexure is variable, but is commonly at first convex, while later the stipes show 

 a decided tendency to grow horizontally. There is nothing approaching the con- 

 spicuous flexure of L. flaccidus and its varieties, var. spinifer and var. macilentus. At 

 their origin the stipes measure 'G mm. in breadth, and widen gradually up to "9 mm . 

 Commonly when compressed the dimensions are slightly in excess of those just 

 quoted, '7 mm. being the width near the sicula and 1 mm. the maximum breadth. 



The sicula has a length of about 1 '0 mm., and 

 is somewhat broad in proportion; th. I 1 originates 

 about "5 mm. above the aperture, and the two cross- 

 ing canals are as a rule wry conspicuous and easier 

 than in some other species, owing to t ho 

 greater breadth of the polypary in its initial region. 



Fig. 68 a. — Leptograptus validus, Laj 

 MS. 



Reverse view. Unlar^vmont, of part of ,,[' detect i< 

 PL XVI, fig. 1 a. 



