28 OLAF HOLTEDAHL. [SEC. ARCT. EXP. FRAM 



JVTollusca. 



Pelecypoda. 

 Prionodesmacea. 



Grammy siidae. 



Grammysia VERNEUIL. 



Grammysia (?) triangulata nov. sp. 



PI. VIII, fig. 8. 



Only one well preserved right valve of a very small lamellibranch 

 of a peculiar type. Placed preliminarly under Grammysia although it 

 differs strongly from the large shells with strong concentric undulations 

 that are most common in this genus. Yet it certainly approaches that 

 genus or to related members of the family Grammysiidae nearer 

 than to any other known groups of lamellibranchs. 



The outline is obliquely and roundly triangular, with the anterior 

 and posterior margin as seen in lateral view meeting nearly at right angles. 

 Except for an abrupt curvature near the margins the shell is nearly flat 

 in longitudinal section, while vertically it is strongly curved, especially 

 in the apical portion. The posterior margin is not wholly preserved, but 

 we see indicated here a sort of minute wing with its plan nearly vertical 

 to that of the shell in general and thus not visible in the lateral view. 

 The surface shows a not strong, but distinct concentric striation and 

 in a good light an indication of radiating striae. 



Dimensions of the valve : length 9 mm., height 7 mm. 

 I do not know of any lamellibranch approaching very near to this 

 form, which may represent only an immature stage. A species which 

 in its younger stages show a considerable likeness, is HALL'S Gram- 

 mysia (SphenomyaJ cuneata from the Hamilton of New York 1 . 



Occurrence: B, upper part, near the fragment-limestone, Valley 

 south of Borgen. 



Aviculidae. 



Pterima GOLDF. 

 Pterinea cf . aviculoidea HALL. 



PI. VIII, fig. 6. 



A left valve of a medium-sized lamellibranch which might possibly 

 be referred to Megambonia aviculoidea HALL from the Manlius of New 

 York and New Jersey 2 , but as the shell is not completely preserved I 



1 See Pal. New York, Lamellibranchiata II, p. 383, pi. 62, figs. 1-9, pi. 93, fig. 19. 



2 See HALL, Pal, New York, vol. 3, p. 274, pi. 49, figs. 7-8, pi. 49 a, fig. 8. WELLER. 

 Geol. Survey of New Jersey, vol. 3, p. 263, pi. 24, figs. 17 18. 



