MONOGRAPTUS. 493 



Monograptus (Rastrites) fugax (Barrande). Plate L, figs. 7 a — d. 



1850. Rastrites fiujax, Barrande, Grapt. de Bolieme, p. QQ, pi. iv, fig. 1. 



Polypary arcuate, with tliecae on the convex margin. Thecse six to eight in 



10 mm., triangular, relatively short and broad, slightly declined, with 



reflexed apertural terminations ; interspaces equal to about twice the length 



of the thecse. 



Description. — The polypary is mostly known in a fragmentary state, but even 



fragments are sufficiently characteristic, with their unusually short and broad thecae. 



The thecEe have an average length of 1 mm.. 



Fig. 348. — Mononraptus (Rastrites) iTiTi ,i -lii cji -i • i , 



fugax (Barrande). and distally the Width oi the mterspaces is about 



^^ 2 mm. The apertural terminations are not un- 



Lj^-^ commonly forked instead of being reflexed, and the 



i_ reflexion is often so slight as to be very incon- 



1 spicuous, and in many states of preservation practi- 



I '"' cally invisible. 



f~^ The sicula has a length of '8 mm. and is con- 



r^ spicuous. Th. 1 originates near its apex, so that, 



F^ as usual, the sicula forms the initial extremity of 



^^>^^ the polypary. 



Affinities. — Perner has considered this form as 

 ^"^laSemenforpa^roFpL L,°^^^ the young of M. {B.) Liniixi with which it is not 



infrequently associated, but in our opinion the thecse 

 are quite different and are not to be regarded as immature thecae of M. (R.) Linnsei. 

 Horizon and Localities. — Birkhill and Gala-Tarannon (zones of M. SedgwicJd 

 and M. turriculatiis) . 



S. Scotland : Belcraig Burn ; Duffkinnel. 



Associates, etc. — M. (B.) fugax occurs somewhat rarely in the highest Birkhill 

 Shales associated with M. {B.) hijhridus, M. Clingani and Glyptog. tamariscus ; and 

 also in the basal beds of the Tarannon Shales with M. (B.) maximus, M. {B.) 

 Linnsei and other forms. 



Collections. — Geological Survey of Scotland, and Lapworth. 



Monograptus (Rastrites) Linnaei (Barrande). Plate LI, figs. 1 a — c. 



1850. Rastrites Linniei, Barrande, Grrapt. de Boheme, p. 65, pi. iv, figs. 2, 4. 

 1897. Rastrites Linnxi, Perner, Grrapt. de Bolieme, iii a, p. 7, figs. 4, 5 ; pi. xiii, figs. 27 — 31. 

 1907. Rastrites Linniei, Toruquist, Rastrites and some allied species of Monograjitus, Lunds Univ. 

 Arsskr., n.s., afd. 2, iii, no. 5, p. 14, pi. ii, figs. 21 — 26. 



