494 



BRITISH GRAPTOLITES. 



Figs. 349 a and h. — Monograptiis (Ras 

 trites) Linnsei (Barrande). 



sj^ 



Polyparj arcuate proximally, with irregular curvature distally. Tiiecae six to 

 four in 10 mm., loug, slightly declined, lengthening gradually from origin 

 till the maximum length of 8 mm. is attained with interspace of about 

 2-5 mm. in extent; base triangular, with slightly swollen apical extremity 

 and slightly reflexed apertural margin. 

 Description. — The polypary is curved somewhat irregularly, but the proximal 

 end appears to be generally arcuate with the thecge on the convex margin. 



The thecse in the proximal portion lengthen gradually, and the interspaces also 



until the maximum thecal leno-th of 8 mm. is 

 attained ; this then remains constant, and the thecae 

 are separated by an interspace averaging 2*5 mm. 

 in extent. The thecee are, therefore, rather more 

 than three times as long as the interspaces. 



Affinities. — Monotj. [R.) Linnsei resembles M. 

 (B.) maxlmus in many respects; it has, however, 

 shorter thecas with a more uniform length, which 

 never exceeds 7 mm., and with interspaces measuring 

 barely 3 mm. in extent. There is, therefore, no 

 such marked and persistent increase in the thecal 

 length as is the case in 71/. (It.) maximus, and the 

 increase in the proximal end is far more gradual 

 than in the latter species. 



Horizon and Localities. — Gala-Tarannon (zone of 

 M. tarricnlatus). 



S. Scotland: Belcraig Burn; Yarrow, etc. C. 

 Wales: Tarannon River; Gelli-dywyll Stream, 

 Llanbrynmair ; Gelli Stream and Pont bren-dibyn, Llanbrynmair ; west side of 

 Upper Quarry, 550 yards E.S.E. of Fuches gau Farm, Pont Erwyd. 



Associates, etc. — Monog. (B.) Linncei is not a common fossil in S. Scotland, though 



it does occur at the base of the Gala beds associated with M. turriculatus, M. nudus, 



M. dextrorsus and M. Halli. It also occurs in Wales in much the same association. 



Collections. — Geological Survey of Scotland, Sedgwick Museum, and the Authors. 





a b 



a. Proximal portion, natural size, for 

 comparison with Britisli specimens. 

 Zelkovitz, Bohemia. Sedgwick Mu- 

 seum. 



h. Distal thecae in relief, showing 

 growth lines. Enlargement of part 

 of PI. LI, fig. Ic. 



Monograptus (Rastrites) maximus (Carruthers). Plate L, figs. 6 a — e. 



1867. Bastrites maximus, Carruthers, Murchison's Siluria, Fossils 90, p. 541, fig. 0. 



1868. Bastrites maximus, Carruthers, Geol. Mag., vol. v, p. 13, pi. v, fig. 14. 

 1876. Bastrites maximus, Lapworth, Geol. Mag. [2], vol. iii, p. 313. 



1876. Bastrites maximus, Lapworth, Cat. West. Scott. Foss., pi. i, fig. 1. 



1907. Bastrites maximus, Toriiquist, Rastrites and some allied species of Monograptus, Lunds Uuiv. 

 Arssk., N s., afd. 2, iii, no. 5, p. 15, pi. ii, figs. 27 — 33, pi. iii, fig. 1. 



