PLAXIPHORA. 481 



Species of Amicula. 



amiculata, Pallas. Pallasii, Midd. 



Emersonii, Couth. vestita, Sow. 



Genus PLAXIPHOEA, Gray. 



Mantle with a double series of pores beset with bifur- 

 cate bristles, one row at the insertion of the valves, the 

 other at the external margin ; mantle-margin smooth 

 and horny, or more or less covered with setose or furfu- 

 raceous scales. 



Shell with the valves broad, transverse, external ; the 

 hinder valve small, with the apex posterior, and with 

 a slight notch on the hind lower edge. 



Syn. Euplaxiphora, Slmttleworth. 



Ex. P. Carmichaelis, Gray, pi. 55, fig. 3. 



In this genus the hinder valve has a slightly-raised, 

 smooth plate of insertion, not divided into lobes at the 

 sides ; the plates of insertion of the middle valves are 

 bi-lobatc, and those of the anterior usually about nine- 

 lobed. 



Sjjecies of Plaxiphora. 



bipunctata, Sow. petholata, Sow. 



biramosa, Qnoy and Gaim. retusa, Soiv. 



Carmichaelis, Gray. 



VOL. I. 3 Q 



