1915- No. 12. THE STROPHOMENIDAE OF THE KRISTIANIA REGION. 87 



Triplecia insula ris Eichw. var. anticostiensis Twenhofel. 

 (PI XVI. %. 10—12). 



1 87 1. Orlliis insuliiris EiCHW. Davidson. Brit. Sil. Foss. p. 273 (in part. ?i. 



1910. Triplecia ortoni Schucmert and Twenhofel. Ord. — Sil. Sect, of the Mingan and 



Anticosti Islands Bull. Geol. Soc. Am, vol. 21, p. 710. 

 1914. Triplecia insitlaris var. anticostiensis Twenhofel The Anticosti Island Faunas. Geol. 



Surv. Canada, Museum Bull. no. 3, p. 26. 



As early as in the publications of X'erneuil and Roemer (see p. 86) 

 it was emphasized that specimens of Spirifcr iiisularis from the Kristi- 

 ania region (Malmo and BryndG\ which they both had studied, differed 

 somewhat from the Russian type specimens. As distinguishing characters 

 are mentioned, that sinus and fold in the Norwegian specimens are more 

 strongly developed and also reach farther towards the beak, furthermore 

 there is a larger size. When looking through the Norwegian material 

 from stage 6,— a very large material of generali}- free, well preserved speci- 

 mens. — I arrived' at the same conclusion as Verneuil and Roemer, 

 viz., that these specimens certainly can be distinguished from those of 

 the Russian L3xkholm division, by the said characters. 



The Norwegian specim.ens from 6 show much variation in their 

 external form. The average sized specimens have a width of about 30, 

 a length of about 25 mm. Sinus and fold may be of very different size 

 in different specimens. In the larger ones they are ver}- prominent and 

 sharply marked with nearly vertical lateral sides. In younger specimens 

 the sinus is much shallover, more rounded, passing more gradually into 

 the rest of the shell, but it is always seen reaching through to the very beak. 



While the beak of the dorsal vahe is always incurved, a fairly high 

 area mav be seen in the ventral valve. Sometimes, however, also the 

 beak of this valve is strongly incurved, so that little of the area is seen. 



A fine concentric striation is always present where the surface is well 

 preserved. 



Occurrence. 6 a — c, Loc. in Bundetjord and Asker. 



Genus Streptis Davidson 1881. 



Streptis nionilifera M'Coy var. altosinuata n. var. 



(PI. XVI, fig. 13-19) 



Mat. pres. A large number of well preserved, free specimens. 

 Description. Size very small, outline broadly oval, cardinal ang- 

 les rounded, hinge line considerablv shorter than greatest width of the shell. 



