504 MYCETOPIN.E. 



Sub-gen. patularia, Swainson (Glabaris, Gray). 



Shell nearly equilateral, round or cordate. Hinge eden- 

 tulous. 



angulata, Lea. Patagonica, Lam. 



anserina, Spix. polita, Moms. 



crassa, Swains. porcifera, Gray. 



Georginae, Gray. sirionos, D'Orb. 



latomarginata, Lea. Spixii, D'Orb. 



Montezuma, Lea. trapezialis, Lam. 

 obtusa, Spix. 



Sub-fam. MYCETOPIN^. 



Labial palps longer than wide. Mantle-lobes disunited 

 as far as the anal aperture, which is closed ; siphonal tubes 

 none; outer branchiae entirely united or grown together. 

 Foot very long, cylindrical, produced and widened into 

 a knob at the extremity. 



Shell thin, gaping at both sides ; beaks nearly central. 

 Hinge linear, straight, toothless. 



Genus MYCETOPUS, D'Orbigny. 



Shell thin, transverse, elongately cylindrical, sub-arcuate, 

 equivalve, sub-equilateral, gaping at both ends, especially 

 posteriorly, covered with an olivaceous epidermis, bluish 

 internally; beaks central, bi-angulated, incurved. Hinge 

 linear, straight, edentulous ; ligament thin, marginal. 

 Muscular impressions somewhat indistinct, composite. 



Ex. M. siliquosus, D'Orbigny,^. 118, fig. .2. Shell, 

 M. soleniformis, D'Orbif/ny, fig. 2, a, 2, b. 



