Observations on the genus Rastrites and some allied species of Monograptus. 



15 



have been observed in the same specimens that also bear thecae of the more mo- 

 derate size; if not, one might be disposed to refer those longer thecse to another 

 species, and most probably to Rastrites maximus Carr. In the distal fragment seen 

 in Barrande's fig. 2, PI. 4, which has an extent of 35 mm., the oldest theca is 7 

 mm. long while the youngest does not exceed 8 mm.; if the length of the following 

 theca? has continued increasing upon the same scale, such a specimen must have 

 attained an extraordinary extent before producing theca? of the size stated by 

 Barrande and Perner. Be this at is may, the first development of Rastrites 

 maximus is too different from that of Rastrites Linneei for these forms to be thought 

 identical. 



In Zjttel's »Grundzüge der Paläontologie, 1895», we find (p. 108, fig. 207) 

 a drawing signed as Rastrites Linncei Barr., but this figure is scarcely referable 

 to any known species. 



Localities and horizon. Thuringia: Rastrites Linnœi occurs abundantly 

 in the zone named after this species; I have seen it represented at Grobsdorf, 

 Rückersdorf, Igelberg and Heinrichsruhe, and Mr Eisel has sent me 

 examples from Raitzhain and Paitzdorf; Bohemia: Barrande's originals 

 were produced from Zelkowitz; Sweden: some poorly preserved specimens, 

 collected at Klubbudden, in the neighbourhood of M o t al a, have been described 

 and figured by Linnarsson; the species is there associated with Monograptus turri- 

 culatus Barr. 



Rastrites maximus Carruthers. 

 PI. II, tigs. 27—33, PI. Ill, fig. l. 



1868 Rastrites maximus Carrdthers, A Revision of the British Graptolites; Geol. 



Mag. Vol. V; p. 13, Pl. V, fig. 14, 



1869 » » Garruihers, Murchison's Siluria, 4:th edition; Appendix 



D, p. 541, Foss. 90, fig. 6. 

 1876 » » Latworth, On Scottish Monograptidie; Geol. Mag. Dec. II, 



Vol. Ill; p. 313. 



1876 » » Lapworth, Gatalogue of the Western Scottish Fossils, PI. 



I, fig. 1. 



1899 » » Frech, Lethsea Geoguostica, I, p. 256, p. 265, fig. 219: 1. 



Only short fragments of Rastrites maximus have been figured up to this date, 

 and therefore, our knowledge of it is, in several respects, deficient. As all the 

 specimens referred to it by me are likewise in a fragmentary state, I think it most 

 suitable to describe some of them individually, leaving to the reader to endorse 

 my determinations, cr not. 



Figs. 28 and 29 present two distal fractions of Scottish specimens from 

 Dobb's Linn, preserved in the Geological Museum of Lund, and labelled by Pro- 

 fessor Lapworth as Rastrites maximus Carr. These specimens have, therefore, 



