igiS- No. 12. THE STROPHOMENIDAE OF THE KRISTIANIA REGION. 3I 



As can only be seen distinctly in the deflected margin, the radiating 

 striae are of two distinct sizes, the distance between two stronger ones 

 varying from i to 2 mm., number of finer striæ counted in one interval 

 was 7, generally somewhat less. In the central disc of the valve these 

 radiating ribs can only be seen near the deflected margin, disappearing 

 towards the beak. This may partly be due to the somewhat worn 

 character of the surface, but it is also to a great extent due to the fact 

 that in the circumbonal region another surface feature is very strongly 

 defined, viz. a large number of small rounded depressions, bordering near 

 to each other, and distributed without regularity. Only close to the hinge 

 line a few of these depressions meet, and form some very short and 

 very irregular wrinkles. In the portion of the central disc that borders 

 on the deflected margin, a few concentric undulations, corresponding to 

 lines of growth, are noticed. 



Observations. In general appearance this form is remarkably 

 like Strophomena elegans Kiesow, found in boulders of Ordovicic rock. 

 The specimen on which that species is founded is, however, only half as 

 large as the one described above. There seems also to be a difference 

 in the character of the surface markings, the rounded and irregular depres- 

 sions in the Norwegian specimen being substituted by »Querrunzeln (nach 

 Art der Strophoiiictia cornigatella Dav.)« according to Kiesow, or »con- 

 centrisch angeordnete Runzeln« (Gagel). A large amount of material might, 

 however, prove the said differences to be of so little value that the forms 

 could be united. 



Occurrence. 4b (4b;'?), Above Bratterud, Bønsnæs, Ringerike. 



Raßnesquina (?) sp. 

 (PI. Ill, fig. 6.) 



The posterior part of what certainly is a ventral valve, besides some 

 tiny fVagments, are all that is present of this form. What can be seen 

 of the shell shows a very slight convexity with a distinct, small, round 

 elevation at the beak itself. Small rounded irregularly distributed depres- 

 sions are all that can be seen of surface markings. 



It is much to be regretted that we do not possess a larger amount of 

 material of this shell, so that the general form might be known. The 

 small fragments that are left point towards a relationship to the form 

 described above, the circumbonal portion of the two specimens being 

 extremely alike. 



Occurrence. 8a, Store, Ringerike. 



