594 



DR. A. MORLEY DAVJES OX THE FAUXAS [vol. lxxix, 



Surface ornamented alike on both valves with close-set, semi- 

 cylindrical, scaly costse. At a distance of 30 mm. from the 

 umbo there are live costas in every 6 mm. The costae increase in 

 number by occasional intercalations, and, at any level, about a third 

 of the cost*, irregularly distributed, are distinctly smaller than 







$ 7 



^ 





CO 

 CJ 



the others, being of late intercalation. In well-preserved parts, 

 line longitudinal striae may be seen both on the costae and in the 

 hollows between them. At intervals of from 1*5 to 3 mm. (the 

 shorter intervals being on the smaller costae) each costa rises into 

 a short thick scale, sometimes semitubular in form. 



