- 116 - 



Remarks .- The peouliar modiolus-like form of this small 

 species at once distinguishes it from the co-existing Areas. It 

 is representel "ny a number of valves; several bein.g slightly larg- 

 er then the tyoe. The shape suggests Oalloarea anri the hincTe Oue- 

 cularia, but the peculiarities of the cardinal area sonnect it 

 most closely with the section Stenoarca. In the ca,;;e of this spe- 

 cies the remarkable features of the carciinal area are even more 

 strongly emphasised than in the other two species of the section. 

 The cardinal area is entirely opisthodetic, exceedingly narrow 

 and so deeply impressed as to be almost internal; indeed, if any 

 portion of the ligament occupied the area below the meriian rid<^-e 

 it may very well have been entirely internal. The teeth are t;;ni- 

 cal of the section in that tbey are divided into two series, but 

 the teeth in the middle of the hinse are very weak or entirely 

 obsolete, leaving only the irregular anterior teeth and the obli- 

 que, regular teeth at the distal end of the posterior series. 



All of the valves are more or less worn, so that the sculp- 

 ture, which is nev- r prominent, is often faint. Several indivi- 

 duals are less inflated throughout and more com-nressed in the 

 posterior dorsal region than the typical form. A. suboandeida is 

 larger, the posterior ridge is less -orominent proxirnally, the 

 slope of the ventral mar-in leys steep, the anterior margin not 

 producer' below an^! the sculpture coarser. 



OcGurrenoe .- lower Miocene: Bowden beds, l^owden, Jamaica. 



