45 
Fam. 12. Placentadce. 
Animal and shell free. Foot cylindrical, compressed, medial, 
without any byssal pore. Vent attached to the right lobe of the 
mantle. Pedal muscle small, having a small round scar between 
the diverging cardinal plates. Lips elongate, attached by their 
hinder edge. Shell compressed. Hinge with two diverging ridges' 
bearing the cartilage. 
1. Placenta (fig. 28). 
Fig. 28 . — Placenta ?. 
a , adductor muscle. /, ligament, h, liver, f, foot, g , generative gland. 
b, muscles suspending the mantle, p, pedal muscle, c, cartilage or 
hinge ridges, i, rectum, v, ventricle, b b, branchio-pallial muscles. 
