no 



■RRTTTSH CIRAPTOLITES. 



curvature is considerable, and it is maintained to the distal extremities. The 

 stipes at their origin have a width of - 4 mm., widening to 1 mm. within a length 

 of 3 cm. 



The sicula measures 1*6 — 2 mm. in length, and 

 th. I 1 seems to originate about %5 mm. above the 

 aperture. Th. I 1 and th. I 2 have slightly mucronate 

 apertures, but none of the thecas subsequently de- 

 veloped show this character. The thecae number 

 nine to eight in 10 mm. ; the free outer walls are 

 curved, are inclined at 15°, and have a length of 

 2 mm. ; they are five times as long as wide, and 

 overlap one half to one third of their extent; the 

 apertural margins are introverted, and occupy one 

 half to one third of the width of the stipe. The 

 free outer walls of the mature thecas are more 

 curved than is usually the case in the Leptograpti ; their more pronounced 

 sigmoid curvature, accompanied by the greater introversion of the aperture, 



approaches the Dicellograptns type of cell. 



Affinities. — L. flaccid us var. macilentus is allied 

 to var. spinifer in general form, but differs from it 

 in the character of the proximal end, in the absence 

 of spines on the proximal thecse, and. in having 

 fewer thecaa in the same unit of length. 



Horizon and Localities. — Lower Hartfell Shales 

 (zone of Pleurog. linearis). 



S. Scotland : Dobb's Linn ; Hartfell Spa. 

 Associates, etc. — -This characteristic variety of 

 L. flaccidus has only been found in the Lower Hart- 

 fell Shales, where it occurs in the zone of Pleurog. linearis, and up to the present 

 time it has been recorded from S. Scotland alone. It occurs at Dobb's Linn and 

 Hartfell Spa, associated with Pleurog. linearis, Leptog. flaccidus, and Diplog. 

 truncatus, var. Several well-preserved specimens are in Lapworth's collection, 

 and a few are in the collections of the Woodwardian (Sedgwick) Museum and the 

 Authors. 



Fig. 64 a. — Leptograptus flaccidus, var, 

 macilentus, Lapw. MS. 



Obverse view. Enlargement of part of 

 PI. XIV, fig-, a b. 



Fig. 64 b. — Leptograptus flaccidus 

 var. macilentus, Lapw. MS. 



Obverse view. Enlargement of part of 

 specimen on same slab as PI. XV, 

 figs. 1 b, c. 



Figs. 64 c and d. — Leptograptus fla 

 var. macilentus, Lapw. MS. 





c. Distal thecaj. Enlargement of part 



of PI. XIV, fig. 3 a. 



d. Distal thecse. Enlargement of part 



of PI. XV, fig. 1 a. 



V;, 



macer, 



now Plate XV, fi <_?s. 2 a — i. 



Description. — Another variety of L. flaccidus characterised by the tenuity of 

 iis stipes lias also been recognised, and to it the name var. macer has been given. 

 Its stipes are 5 — 7 cm. or more in length, they are commonly directed upward and 



