16 



Sv. Leonh. Törnquist. 



been taken as standard ones. The more perfect of them (Fig. 29) measures 13 

 mm., in extent, and gives off four thecœ. Ttiese have a length of 10 or 11 mm., 

 are gently curved, and perceptibly reclined. A triangular dilatation, though shorter 

 than that seen in JRastrites Linnœi, is visible at their bases, and their very extre- 

 mities are also a little widened. The internodes average 4 mm. in length. In the 

 other example from the same locality the internodes are but 3 mm. long. 



The very sicular portion, as seen in an example found by me at Dohb's 

 Linn, is delineated in fig. 27. It shows quite the same hook-shaped form as the 

 corresponding part of Rastrites peregrinus and of some other Rastrites, the sicula 

 being indicated by a small triangular widening of the initial extremity. The first 

 internode is very short, and the three following ones augment successively to 1.5 

 mm., 2 mm. and 2.5 mm. The four thecae first developed seem to be broken off; 

 the fifth, again, has a length of 4.5 mm. and the sixth, of 5.5 mm. Their form 

 agrees precisely with that seen in the specimens just described. 



In figs. 31 and 32 two specimens from Motala are illustrated, that seen in 

 fig. 32 being unusually clear. It represents an early stage of development, though 

 the very extremity is wanting. The gradual increase in length of the thecae and 

 internodes visible may be inferred from this table 



Length of thecae visible Length of internodes visible 



I II III IV I II III IV 



1 mm. 2.7 mm. 6.2 mm. 1.7 mm. 1 mm. 1.4 mm. 1.7 mm. 2 mm. 



In spite of its shortness the fourth theca is not broken off, whence it may 

 be concluded that the growth of the rhabdosome has been interrupted a short time 

 after the budding of this theca. 



The specimen from which fig 1, Pl. Ill has been drawn, was found by me at 

 Heinrichsruhe in Thuringia. It is a portion of the adult region, having a 

 length of 28 mm., and bearing 9 thecae. These have an almost rectangular posi- 

 tion w r ith respect to the stem, and are, when unbroken, about 12 mm. long. The 

 internodes have a width of .25 mm., and the diameter of the middle part of the 

 thecae is .5 mm.; both being strongly compressed. 



In an earlier paper 1 ) I have recorded the two specimens from Motala as 

 Rastrites Linnœi Barr., and, as already mentioned, Perner holds it far from im- 

 probable that the species Rastrites maximus was founded on distal fragments of 

 that species. If I am right in my interpretation of the examples dealt with in the 

 above, Rastrites maximus is, however, well distinguished by (1) a different form of 

 the proximal part and (2) a more rapid increase of the consecutive earlier thecœ. 



Horizon. As the localities which have afforded the examples described have 

 already been given, it should only be added that the species everywhere is confined 

 to an horizon near the top of the Rastrites-be&v'mg shales. 



') Törnquist, Berättelse om en geologisk resa genom Skånes och Östergötlands paleozoiska 

 trakter, sommaren 1875; Öfvers. af K. Vetenskaps-Akad:s Förhandl. 1875; p. 68, 69. 



