488 BRITISH GRAPTOLITES. 



Monograptus (Rastrites) peregrinus (Barrande). Plate L, figs. 1 a — e. 



1850. Rastrites peregrinus, Barrande, Grapt. de Boheme, p. Q7, pi. iv, fig. 6. 

 1892. Rastrites peregrinus, Tornquist, SiljansomrM. Grapt., ii, p. 2, pi. i, fig. 1. 

 1899. Rastrites peregrinus, Perner, Grapt. de Boheme, iii a., p. 8, fig. 6 ; pi. xiii, figs. 33, 34. 

 1907. Rastrites peregrinus, Tornquist, Genus Rastrites and allied species of Monograptus, Lunds 

 Univ. Arsskr , n.s., afd. 2, iii, no. 5, p. 6, pi. i, figs. 1 — 22. 



Polypary small, arcuate, with short sharply recurved proximal portion. Theca& 

 eight to ten in 10 mm., from 1 — 2'5 mm. in length, with narrow inter- 

 spaces, somewhat club-shaped, with apparently rounded extremities owing 

 to the very slight apertural reflexion. 

 Description. — The polypary never seems to exceed 3 cm. in length, so that it is 

 characteristically small, and as Tornquist has pointed out, its proximal portion is 

 "recurved so as to present the shape of a small fish-hook"; he also lays some 

 stress upon the direction of growth of the early thecse, but this does not appear 



to us to be at all constant, varying very much with 



Fig. 343. — Monograptus {Rastrites) , . , , . . 



peregrinus (Barrande). conditions ot preservation, tliougli it IS true that as 



a whole the distal thecse are distinctly declined. 



The sicula is inconspicuous. 



Though the thecge in the proximal portion do 

 not exceed 1 mm. in length, they quickly reach 

 their maximum length of 2*5 mm., which is main- 

 tained thereafter. The width of the interspaces 

 between successive thecj© is generally 1 mm. in 



Proximal portion, showing part of the extcilt. 



sicula. Skelgill, Lake District ; Skel- mi i i i i n • • ^ 



gill Beds. Sedgwick Museum. T lie tliecsB themselvcs have a characteristic shape,. 



appearing narrow at their bases, then widening and 

 then diminishing again towards their terminations, which are generally rounded 

 off, the result being a somewhat club-shaped appearance. There is only a slight 

 trace of reflexion of the apertural region, which shows itself as a terminal 

 rounding off when the reflected portion is turned away from the observer. 



Affinities. — Many of the different forms included in this group (Uiutrites) have- 

 at one time or another been referred to Monog. (B.) peregrinus ; there can be little 

 doubt, however, that this name should be (as recognised by Perner and Tornquist) 

 restricted to those forms which are small and which have short club-shaped thecfe 

 situated at fairly close intervals. M. (R.) lii/hridus, which perhaps comes nearest 

 to M. (E.) peregrinus in point of size, is distinguished by the far more definitely 

 reflexed apertural terminations. 



Horizon cx'tid Localities. — Llandovery (zones of M. gregarius and M. convolutus) . 



S. Scotland: Dobb's Linn; Garple Linn; Belcraig Burn, etc. Lalce District: 

 Skelgill. Ireland : Coalpit Bay, Donaghadee. 



