84 PHYSAD A. 
Subfamily MrcasistropHin.£, Tryon. 
MecasystropHa, Lea.* 
4, Shell dextral, discoidal, whorls visible 
above and below. 
Subfamily PLANoRBINA. 
Aperture unarmed, Puanorsis, Guettard. 
Aperture toothed within, 
SrcmEntInA, Fleming. 
5. Shell non-spiral, conical, patelliform. 
Subfamily ANcYLinz. 
* Base or aperture oval, entirely open. 
Apex directed to the right, 
Ancytus, Geoffroy. 
Apex directed to the left, 
AcroLoxus, Beck. 
* Base partly closed by a horizontal lamina. 
Apex directed backwards, 
GunpLacuia, Pfeiffer. 
*Mr. Binney’s name Carindfex is generally quoted for 
this genus, but Mr. Lea’s name has priority. It is true that 
Mr. Binney used the name at an earlier date in some proof 
sheets, but he requests in the preface that they shall ‘ not 
be quoted as authority, or referred to as a published work.” 
I yield to Mr. Binney’s request. 
(58) 
