- 490 - 



6 rnm. in altitude and 2 mm. in diameter, whereas the lar/rest valve 

 of the latter has these 'imensions: length 6.5 mm.; alt., 5 mm.; 

 diam. , 2 mm. Althori~h the aversfre hender s oni is less inflated 

 than simpsoni , ao;:ie vaj.ves ^ re erually inflated. T_. aelontea 

 )all (1) from the Ohipola marl, is smaller, less inflated, and 



(1). oe. oit., p. 1D25, pi. 46, fig. IG, 19 '.O. 



more elon<?ated. 



Occurrence. - lower Miocene : Bowden beds, iovrden, ''amaica 

 (Ball, 1900). 



