14 



Sv. Leoni). Törnquist. 



Rastrites Linnsei Barrande. 

 Pl. II, figs. 21—26. 



1850 Rastrites Linncei Barrande, Graptolites de Bohême, p. 65, Pl. 4, figs 2, 4. 



1850 » fugax » Ibid. p. 66, Pl. 4, fig. 1 (teste Perner). 



1851 Graptolithus Linnœi Suess, Ueber Böhmische Graptolithen, p. 42, Taf. IX, 



fig. 14 b (? 14 a). 



1852 Monograptus Linnœi Geinitz, pars, Die Graptolithen, p. 48, Taf. V, fig. 19. 



1853 » » Richter, Thüringische Graptolithen; Zeitschr. d. Deutsch. 



Geolog. Gesellschaft, Bd 5; p. 462, compare p. 445. 

 1881 Rastrites Linnœi Linnarsson, Graptolitsk. med Monogr. turriculatus vid Klubb- 

 udden; Geol. Foren, i Stockholm Förhandl. Bd V; p. 520, 

 Tafl. 23, fig. 22, 23. 



1890 Monograptus Linnœi Geinitz, pars, Die Graptol. d. K. Mineralog. Museums 



in Dresden, p. 22, Taf. A, fig. 33. 

 1897 Rastrites Linnœi Perner, Etudes sur les Graptolites de Bohême, IlLieme 



Partie, Section a, p. 7, fig. 4, 5, Pl. 13, figs, 27—31. 

 1897 » » Frech, Lethœa Geognostiea, Bd. 1, p. 665, fig. 219:5. 



1899 » » Eisel, Die Schichtenfolge d. ostthüring. und Vogtland. Grapto- 



lithenschiefer, p. 6. 



According to Perner the proximal portion of this species is identical with 

 Barrande's Rastrites fugax. It is slightly arcuate and produces thecee which are 

 somewhat reclined and shorter than their interspaces. After a gentle bending the 

 rhabdosome continues in a distal division which tends to become straight, and 

 displays an appearance so different from that of the initial part that Barrande, 

 who had not seen these parts connected, described them as separate species. Gei- 

 nitz suggested, however, already in 1852 that Rastrites fugax seemed to be what 

 he called »der Jugendzustaud» of Rastrites Linnœi 1 ). I have had no opportunity of 

 examining the sicular portion, but several of my specimens exhibit the transitional 

 curvature. In this the length of the consecutive thecœ augments from 1.5 mm. 

 to 4 mm.; in the remaining part of the rhabdosome this length increases more 

 slowly. As far as I have observed, the thecee number, in the mature region of 

 the rhabdosome, 4 or 3.5 in the space of 10 mm., reaching a length of from 5 to 

 8 mm. according to their place. In some cases they stand normal to the stem, 

 but more frequently they show a downward inclination. Their bases are dilated 

 so as to form scalene triangles elongated in the direction of the thecse, and they 

 widen, likewise, though more abruptly, towards the apertural ends. 



Barrande states that he has seen isolated thecae measuring as much as 16 

 mm. in length, and according to Perner the distal thecse reach a length of 15 

 mm. 2 ). From Perner's description it cannot be inferred whether these long thecse 



') Geinitz, Die Graptolithen, p. 49. 



2 ) Barkande, loc. cit. p. 65, 66. — Pebnek, loc. cit. p. 8. 



