34 
Fam. 4. Pisidiadce. 
Pedal and branchial openings inferior. Foot lanceolate, com- 
pressed, not byssiferous. Siphons conical, more or less elongate. 
Gills two on each side. 
1. PlSIDIUM. 
1. P. amnicum, t. 349. f. 1, 10 (fig. 17). 
Fig. 1 7 . — Pisidium amnicum. 
2. P. Henslowianum, t. 351. f. 8. 
3. P. pusillum, t. 351. f. 3, 7, 10. 
4. P. obtusale, t. 351. f. 1. 
5. P. nitidum, t. 351. f. 4. 
6. P. pulchellum, t, 351. f. 2, 5, 6. 
Order IV. Unionacea. 
Mantle lobes free, slightly united behind, forming a separate anal 
siphonal opening placed under the hinder adductor muscle. 
Suborder I. Lucinacea. 
Foot cylindrical, elongate, inferior. Anterior adductor muscle 
generally elongate. 
Fam. 1. Lucinidce. 
Anal siphon elongate, cylindrical, retractile into the mantle cavity. 
Pedal opening inferior, moderate. Gills only one on each side of 
the body, lamellar, oblong, broad, united behind the base of the 
foot. Foot cylindrical, elongate, inferior, not byssiferous. Lips 
none. Mantle double-edged; outer dilatile. — See Ann. fy Mag. 
N. H. xiv. 1854, 25. 
1. Loripes. 
1. L. lactea, t. 355. f. 1, t. 356. f. 5. 
2. Lucina. 
1. L. luteola, t. 356. f. 6. 
2. L. columba, t. 355. f. 2. 
3. L. jamaicensis, t. 354. f. 2. 
4. L. tigerina, t. 354. f. 1. 
