106 BRITISH GRAPTOLITES. 



Leptograptus flaccidus (Hall). Plate XIV, figs. 1 a— g. 



1865. Graptolithus flaccidus, Hall, Grapt. of Quebec Group, Suppl., p. 143, pi. ii, figs. 17 — 19. 



1867. Non Didymogrwpsus flaccidus, Nicholson, Geol. Mag., vol. iv, p. Ill, pi. vii, figs. 1 — 3. 



1870. Non Didymograpsus flaccidus, Nicholson, Ann. Mag. Nat. Hist. [4], vol. v, p. 353, pi. vii, 



fig. 6. 

 1876. Leptograptus flaccidus, Lapworth, Cat. West, Scott. Foss., pi. iii, fig. 73. 



Stipes narrow, flexed, several cm. in length, widening gradually and per- 

 sistently from their origin to a maximum width of about 1 mm. Sicula 

 1'5 — 1"6 mm. in length. Thecas uniformly narrow, ten to eight in 10 mm., 

 inclined at 15°, seven to eight times as long as wide, free two thirds to one 

 half their length. Apertural margins narrow, straight, or slightly concave 

 when compressed, submucronate, very slightly introverted. 

 Description. — The stipes characteristically show graceful double curvature in 

 their more proximal parts ; close to the sicula they are convexly curved with 

 respect to their ventral margins, and then bend outward and upward with a concave 

 sweep, running ultimately in an approximately horizontal direction ; this curvature is, 

 however, by no means constant in amount. The stipes widen gradually throughout 

 the first five or six centimetres of their length, from a width of '5 mm. opposite the 

 aperture of the first theca to a maximum width of about 1 mm., which is thereafter 

 maintained. The stipes must frequently have been exceedingly long, since frag- 

 ments having a length of 8 — 10 cm. are of frequent occurrence, and that these belong 

 to the distal parts of the stipes only is evidenced by their uniform breadth. 



The sicula measures 1*5 to 1*6 mm. in length. The first theca (th. I 1 ) appears 

 to originate at a point about *5 mm. above the base ; it grows at first vertically 

 downward, but then bends sharply round almost at right angles, so that its 

 apertural part is perpendicular to the long axis of the sicula, and the aperture itself 



is approximately parallel to it. In the reverse 



Kins. Cii' a uiiil b.— Iji'jitoiinqitus flaccidus 



(Hail). aspect of the polypary only a small part ot the 



apertural region of the sicula is visible below the 

 outer walls of th. I 1 and th. I 2 ; the crossing canal 

 (c.c. 1 ) is seen to be but very slightly oblique, and 

 the aperture of th. I 2 lies on the same level as that 

 of th. l l , giving a very symmetrical appearance to 

 the proximal end as a whole. Another characteristic 

 „ _ , . . feature of this reverse aspect of the polypary is 



a. Reverse view. Enlargement <>t pari r r J r J 



"' ''' X| v,iie;. i b. the mode of growth of th. I 2 , which almost entirely 



b. Proximal extremity, showing rum- ... 



piete sicula. Enlargement of part conceals the initial part of th. I 1 . The appearance 

 of ii. \iv, ti-. i „ _ i _ * * 



of the polypary also clearly indicates the presence 



