ACROLOXUS. 231 



Genus ACROLOXUS, Beck. 



A. Eastern Species. 



1. ACROLOXUS OVALIS, Morse, 



Plate 2, figs. 5, 6. 



Shell very small, depressed, irregularly 

 ovate, apex nearly central, round, smooth and 

 blunt, slightly inclined to the left; slopes 

 irregular, caused by different periods of repose 

 and growth ; posterior slope in most speci- 

 mens straight, anterior slope convex, lateral 

 slopes steep ; shell widening anteriorly ; lines 

 of accretion extremely fine, visible within but 

 requiring a magnifier to discern them without, 

 being greatly obscured by fine grains of sand 

 agglutinated to the surface. Periostraca pale 

 yellow ; the surface, when magnified, exhibits 

 about forty-five delicate ribs, which radiate 

 from the apex to the periphery of the shell. 



Length 3, width 2-5, alt. 1*5 mill. 



Androscoggin River, Maine. 

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