46 



OLAF HOLTEDAHL. M.-N. Kl. 



seen from the section plate VI, fig. lo. The surface ornamentation con- 

 sists of numerous, fairly prominent radiating striae, between two of which 

 come from 4 to 8 finer ones. Crossing the radiating striae, we notice at 

 places where the surface character is clearly visible, crowded concentric 

 lines. No wrinkles or corrugations are present. The preservation of the 

 posterior part of the mould is, however, not good as will be seen from the 

 illustration. 



Observations. As only this single and incomplete specimen 

 is at hand, I should not have dared to give it any specific name, 

 had I not among the Russian material, that I obtained from Petrograd, 

 found a number of complete specimens that without doubt are identical 

 with the specimen described above. One of the Russian specimens was 

 labelled by the late Fr. Schmidt as Strophomena hemispherica ^ a name 

 that therefore will be retained. The horizon of the Russian specimens 

 according to the label is B II -III of the Ordovicic series of Western Russia. 

 As this Russian material will be the object of separate studies I will not 

 here go into detail as to the characters of the Russian specimens. 



To judge from the exterior of the ventral valve, the form described 

 above is extraordinary like a form of very much younger age, viz. Stro- 

 phonella euglypha Dalm. As can be judged from the Russian specimens, 

 however, the two forms show a distinct difference in form of the dorsal 

 valve. 



Occurrence. 3c ^. Killingen, near Kristiania. 



Strophomena (?) Jentzschi Gagel. 

 (PI. VI, fig. I.) 



1890. Strophomena Jetitsschi Gagel, Die Brachiopoden der cambr. u. sil. Geschiebe p. 44, 



pi. V, fig. 26. 

 1905. Strophomena Jentsschi W. Lamanskv, Die ältesten silur. Schichten Rufslands. Mém. 



Com. Géol. Nouv. Ser. 20, p. 171 and 177. 

 1907. Strophomena Jentzschi Wiman, Studien über das Nordbaltische Silurgebiet II. Bull. 



Geol. Inst, of Upsala. Vol. VIII, p. 103. 



Mat. pres. One fairly complete outer mould of a ventral valve 

 and a broken, strongly worn dorsal valve. 



Description. Size small, outline broad, with acutely projecting 

 cardinal extremities. Circumbonal portion of ventral valve rather flat, 

 with a slight elevation at the beak; frontal portion rather abruptly 

 •deflected with an angle of about 120*'. Length of the deflected border is 



' The dorsal valve of the Russian specimens being roundedly and evenly gibbous, corre- 

 sponding to the name. 



