32 
2. M. arenaria, t. 348. f. 1, 4, 
(%• 16). 
2. Sphenia. 
1. S. Binghami, t. 372. f. 5. 
Fam. 7- Corbulidfp. 
Siphons moderate. Foot small. 
Gills two on each side, dependent, 
separate, moderately prolonged. 
Lips long. Shell porcellanous. 
Hinge with a conical tooth and a 
cartilage-pit in each valve. 
1. CoRBULA. 
1. C. nucleus, t. 350. f. 4. 
2. C. patagonica, t. 350. f. 1. 
3. C. mediterranea, t. 350. f. 6. 
2. Azara. 
1. A. labiata, t. 350. f. 7- 
Fam. 8. Pandoridce. 
Siphons large. Foot moderate. 
Gills subpinnate, one on each side, 
greatly developed. Lips long. 
Shell pearly. Hinge with two di- 
verging teeth and a triangular car- 
tilage-pit in each valve. Valves 
very unequal. 
1. Pandora. 
Fig. 16 . — Mya arenaria. 
1. P. oblonga, t. 372. f. 11 
2. P. obtusa, t. 350. f. 5. 
3. P. rostrata, t. 350. f. 8. 
Left half of mantle andshellremoved. 
a a', adductor muscles, b, body. 
c, cloaca, f, foot, g, gills, h, 
heart, m, cut edge of mantle, 
o, mouth. s s, siphons. labial 
tentacles, v, vent. The arrows 
indicate the directions of the 
currents. The four rows of dots 
at the base of the gills are the 
orifices of the branchial tubes 
opening into the dorsal channels. 
