19 1 5- No. 12. THE STROPHOMENlD,AE OF THE KRISTIANIA REGION. 33 



lateral margins. Radiating striae as well as the irregular wrinkles are of 

 nearly the same type in both. 



Occurrence, ^d, Frogno, Ringerike. 



Raßnesquina(?) semipartita Roem. 

 (PI. Ill, fig. 3-4.) 



186 1. Strophoiiiena semipartita F. Roemer, Die fossile Fauna der Sil. Diluvial-Geschiebe 

 von Sadewitz bei Oels, p. 43, pl. V, Fig. 9, a, b, c. 



A few ventral and some outer moulds of dorsal valves, all fragmentary, 

 must be referred to this species, which I know besides from Roemers 

 descriptions and figures from a large number of Russian specimens. 



This is certainly an extremely varying form both in outline and in 

 convexity. 



The Russian specimens are usually more evenly convex, — globose, 

 than the Norwegian ones, the latter having a somewhat more marked geni- 

 culation in both valves, especially in the dorsal. The radiating striæ are 

 fairl}' uniform and rather well-marked, some of them, especially in the median 

 portion, stronger than the rest. Most of my specimens, however, are 

 rather poorly preserved, so that the detailed characters cannot be well 

 studied. The concentric corrugations are most distinct in the circumbonal 

 region, especially near the hinge, being obsolete in the latero-frontal 

 portion of the specimens. 



Occurrence. 5a, Ringerike; Asker; Skien — Langesund district. 



Genus Stropheodonta Hall 1852. 

 Subgenus Brachyprion Skaler 1865. 



Brachyprion (?) pseudeuglypham Gagel (?). 

 (PI. IV, fig. I, pl. XVI. fig. I.) 



1884. Styophomena euglypha Kiesow. Ueber sil. 11. dev. Geschiebe Westpreufiens. Sehr, 



d. natiirf. Ges. in Danzig. N. F. B. 16, p. 48. 

 1890. Strophonieiia pscitdetiglypha Gagel. Brach, d. cambr. u. sil. Geschiebe elc, p. 45, 



pl. III, fig. 16. 



Mat. pres. A few usually broken ventral valves and a fragmen- 

 tar}' mould of a dorsal valve. 



Description. Shells of small size, somewhat variable. Outline 

 broad, with rather acute cardinal extremities. Width and length of some 

 specimens are given here in millimeters: 



Width 15 18 26 



Length 9V2 11 16 



Vid.-Selsk. Skrifter. I. M.-\. Kl. 191 5. No. 12. 3 



