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



IVEollusca. 



Pelecypoda. 

 Prionodesma,cea. 



Grammy siidae. 



Grainmysia 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 preliniinarly under Grammijsia 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 lameliibranchs. 



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 (Sphenomya) cuneata from the Hamilton of New York i. 



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

 south of Borgen. 



Aviculidae. 



Ffrrinea Goldf. 



Pteri)iPa cf. avicnioiden Hall. 



PI. Vm, fig. 6. 



A left \'alve of a medium-sized lamellibranch which might possibly 



be referred to Megambonia aricnloidea Hall from the Manlius of New 



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



1 Sei' Pal. Nrw York, Lamellibrancluata II, p. .38-3, pi. 62, figs. 1-9, pi. 03, fig. 19. 



2 See Hall, Pal, New York, vol. 3, p. 274. pi. 49, fig.s. 7-8, pi. 49 a, fig. 8. Wkller. 

 Geol. Survey of New J.^rsey. vol. 3, p. 263, pi, 24, figs. 17-18. 



