18 



Sv. Leonh. Törnquist. 



Monograptus cfr. urceolus Richter. 

 Pl. III, figs. 5—10. 



1853 cfr. Monograptus urceolus Richter, Thüringische Graptolithen ; Zeitschr. d. 



Deutsch. Geologischen Gesellsch., Bd 5; p. 462, Taf. 

 12, figs. 29, 30. 



1899 Rastrites urceolus Eisel, Die Zonenfolge d. ostthüring. u. Vogtland. Grapto- 



lithenschiefer; p. 6. 



The diversity of aspects presented b} 7 this species can most easily be accounted 

 for if the rhabdosoine is supposed originally to have been rolled up into a conical 

 spiral. My best preserved specimens have a length of about 40 mm. with an 

 average width of 1.5 to 2 mm. The common canal is narrow, though not so 

 uniformly threaddike as that of the Rastrites. Owing to the effect of pressure, 

 the number of thecœ to a given unit varies considerably even in different parts 

 of one and the same volution, but, when least deformed, 11 or 12 can be counted 

 in 10 mm. Those originating from the earliest coil are isolated, whereas the suc- 

 ceeding ones assume a triangular form and come in contact with one another. 

 All have originally terminated in reflexed lobes, which, on account of different 

 directions of the pressure, are larger or smaller, or even protracted and pointed. 



From Monograptus convolutus His. and M. decipiens Törnq. the species is 

 readily distinguished by (1) the conical growth of the helicoid rhabdosome (2) the 

 form and size of the thecœ. From Monograptus proteus Barr, it differs in the 

 structure of its initial part. 



Eisel has identified this species with Monograptus urceolus Richter. The 

 figures given by the last-named author deviate not a little from the examples in 

 my possession, it is true, but, nevertheless Eisel's identification may, possibly, be 

 well founded, for the general habit of the species is exceedingly variable. When 

 the monograph of Thuringian graptolites which Mr Eisel lias been preparing for 

 many years, is published, our knowledge of this species, as well as of many others, 

 will certainly be much enriched. 



Localities and horizon. Thuringia: The species described is a very 

 common one in the zone of Cephalograptus conieta (zon 14), as exposed at Grobs- 

 dorf (Eisel, Törnqüist), Raitzhain (Eisel), &c. 



Note. There occur at Heinrichsruhe, in Thuringia, high up in the Rastrites 

 series, numerous small graptolitic fragments, some of which are represented in figs. 

 11 — 15, on PI. III. I have seen no longer fragments than those figured; nor have 

 I discovered associated with them greater specimens of which they could be thought 

 to be fragments. They are all moderately curved, giving rise to thecse from their 

 convex margin. The thecse number from 7 to 9 in the space of 5 mm. (14 to 18 

 in 10 mm.), are 1 mm. long, perpendicular to the stem, and provided with short 

 reflexed apices. If we disregard the higher number of thecse to a given length, 

 these fragments bear an unmistakable resemblance to the proximal portion of the 



