Sv. Leonh. Törnquist. 



DESCRIPTIONS. 



Genus Rastrites Barrande. 

 Rastrites peregrinus Barrande. 

 Pl. 1, figs. 1-22. 



1850 Rastrites peregrinus Barrande, Graptolites de Bohême, p. 67. Pl. 4, fig. 6. 

 1892 » Törnquist, Undersökn. öfver Siljansområdets Graptoliter 



II; K. Fysiogr. Sällskapets Handl. Bd 3 (Acta Univ. Lund., 



Tom. XXVIII); p. 2, Tafl. 1, fig. 1. 

 1899 » » Perner, Etudes sur les Graptolites de Bohême, Ill ,ime 



Partie, Section a; p. 8, fig. 6, Pl. 13, figs. 33, 34. 



From an initial portion recurved so as to present the shape of a small fish- 

 hook, the rhabdosome proceeds in a slightly arcuate distal part, which attains a 

 length of, at least, 30 mm., and emits thecse from its convex margin. The sicula 

 is in some specimens indicated by a triangular widening visible at the proximal 

 extremity of the rhabdosome. It seems to have reached as far as a little above 

 the inner orifice of the first theca. The three or four thecse first developed are 

 directed a little upward, and are sometimes followed by two or three others stand- 

 ing normal to the common canal; all the succeeding ones are perceptibly reclined, 

 forming with the internodes next below angles of 60° to 70°, or, near the distal 

 end, of 80° to Sô n . They number from 8 to 10 in the space of 10 mm., the inter- 

 vals between them being in the majority of specimens precisely 1 mm. The 

 length of the thecse augments from 1 mm. near the sicula to 2 mm. in the adult 

 region. In compressed condition they have an average diameter of .3 mm., and 

 are sometimes slightly dilated toward their extremities, which are rounded or trun- 

 cated, but never reflexed as in the following variety. The width of the common 

 canal varies between .15 and .2 mm. according to the amount bf compression. 



A comparison between the specimens from Bohemia delineated in figs. 1 — 8, 

 and those from different parts of Sweden and Great Britain drawn in figs 9 — 20, 

 will evince the constancy of the characters given in the above description and may, 

 at the same time, give sufficient reason for separating from Rastrites peregrinus 

 Barr. several forms, from time to time, recorded and figured under that name. 

 In confining the species I have followed Perner altogether. 



This author is, however, I think, hardly right in rejecting my identification 

 of a graptolite from Dalarne with Rastrites peregrinus (loc. cit. suprà). In support 

 of his opinion he puts forward the assertion that the internodes of the Dalecarlian 

 form have a length of 1.5 mm. In fact, the topmost internode seen on Pl. I, fig. 

 1 of my paper cited has that length, probably owing to a misdrawing, but all the 

 remaining ones are shorter; moreover, in the diagnosis of the species I have ex- 

 pressly stated the number of theca? in 10 mm. to be from 8 to 10, the last num- 



