HISTORY OF RESEARCH. 



XC1X 



1880. 



Tornquist, 



' Studier ofver Retin- 



lifes," ' Geol. Foren. 



F6rh.,' btl. 5. 



A most important paper by Tornquist bearing on the 

 structure of Retiolites appeared in 1880. By means of 

 sections, transverse and longitudinal, he was able to elucidate 

 many points which Linnarsson, Barrande, Hall and others 

 had left unsettled. His materials consisted not only of 

 specimens of the true Retiolites, but also of another form, 

 which was separated later by Tullberg as a distinct genus — Stomatograptus. 



Structure. — The main result arrived at by Tornquist is that the polypary in 

 these genera consists of two different elements : (1) " the outer polyparium or 

 periderm, consisting of the reticulate skin, with its parietal and apertural threads, 

 strands, and two virgulas ; (2) the inner polyparium, with smooth and thinner 

 walls." 



The inner polyparium is very similar to that of a diprionidian Graptolite, and 

 possesses distinct interthecal walls of a trough-like shape. The thecao arise from 

 an extremely narrow common canal, and open outward and upward. 



This inner polyparium was presumably attached to the outer in such a way that 

 " the free wide thecal apertures of the former are fastened to the parietal threads 

 of the latter." 



The network-like periderm, which may have been covered by a thin skin, is not 

 in close contact with the inner polyparium, and the space between the two 

 Tornquist calls the " parietal canal." 



CHAPTER IV. 



1881 to 1907. 



Tornquist, in the year 1881, described and figured five 

 new species of Monograptus from the Retiolites shales of 

 Dalarne. These are M. cultellus, M. nodifer, M. crenulatus, 

 M. continens, and M. sartorius. In addition to these he 

 figures and describes specimens of Diplog. folium, D. pristis, 

 and Monog. priodon. 



The same year Linnarsson described a number of Grapto- 

 lites from Klubbudd in beds which he considers answer in 

 stratigraphical position to the Lower Gala of Scotland. Four 

 of his species are given as new, viz. : Monog. rhyncophorus, M. 

 dextrorsus, M. tortilis, and M. resurgens. The other species 

 described and figured by Linnarsson are : M. jaculum, M. 

 priodon, M. cf. crassus, M. cf. lobifer, M. runcinatus, M. turri- 

 culatus, Rastrites IAnnrni, Biplograptus palmeus, and Retiolites perlatus ? 



1881. 



Tornquist, 



" Om u:\gra graptolit- 



arter fran Dalarne," 



' Geol. Foren. Forh.,' 



1x1. 5. 



1881. 



Linnarsson, 



" Graptolitskiffrar med 



Monoqraptus turricu- 



latus vid Klubbudden 



niira Motala," ' Geol. 



Foren. Forh.,' bd. 5. 



