LEPTOGRAPTUS. 115 



cremate and introverted ; they occupy two-thirds to one-half of the entire breadth 

 of the stipe. 



Affinities. — -Var. incisus is characterised by t\w tenuity of its stipes, the length 

 of its sicida, and the great width of the apertures of its thecae relatively to the 

 breadth of the stipe. As regards the tenuity of its stipes, var. incisus somewhat 

 resembles L. fiaccidus, var. macer, but differs in its mode of growth and in the 

 characters of the thecse. 



Horizon and Localities. — Glenkiln Shales. 



8. Scotland : Sowen Burn, Wanlock Head. 



Associates, etc. — Var. incisus occurs but rarely in the Glenkiln Shales of S. 

 Scotland, where it is found associated with the typical Glenkiln fauna. 



The best specimens, including- the type, are in Lap worth's collection. 



Note. 



In addition to the forms of L&ptograptus just described, there occur in the 

 Skiddaw Slates of the Lake District numerous fragments the specific deter- 

 mination of which is inadvisable, if not impossible. 



The thecse on these fragments are well seen, and are clearly of the Leptograptid 

 type, but the stipes are so fragmentary that it is impossible to imagine their 

 original sweep. These are therefore figured (PI. XVI, figs. 3 a, b), but not 

 described. 



Horizon and Localities.— U pper Skiddaw Slates (Ellergill beds). 



Lake District : Basseiithwaite Sand-beds : Aik Beck. 



Leptograptus grandis, Lapworth MS. Plate XVI, figs. -4 a — (/. 



Stipes robust, somewhat rigid, 3 — 4 cm. (or more) in length, widening gradually 



from origin, and diverging from the middle of a fairly conspicuous sicula so 



as to include an angle of about 210°. Thecal ten to nine in 10 mm., inclined 



at 10°, six times as long as wide, free about one-half their length. Apertural 



margins submucronate, straight or slightly concave when compressed, 



slightly introverted, occupying one-half to one-third the breadth of the stipe. 



Description. — The stipes are somewhat rigid, but may occasionally be stiffly 



Pigs. 70« and b.-Leptograptus grandis, Lapw. curved ; they are '6 mm. wide at their origin 



Ms - and increase up to a maximum breadth of 



1 ^df ' - i» rather more than 1*5 mm, 



^'^Xvr^-' 1 ^v^v m] 1(3 s j cu i a i s fairly long, it has a length 



a h of 1*5 — 1*6 mm., and is broad in proportion. 



a. Obverse view. Enlargement of part of PL rp^e origin of the si iocs is sublliediail. mid 



XVI, n^'. t 'I. ° L 



b. Reverse viow. Enlargement of part of PL XVI, fj 10 theClC gl'OW outward and slightly down- 



