SEMELIDA. 163 
Syn.—Amphidesma, Lamarck, 1818. 
Distr.—60 sp. West Indies, Brazil, India, China, Australia, 
Peru. Fossil, 30 sp. Eocene—; United States, Europe S. 
variegata, Lam. (ex, 34). 8S. reticulata, Chemn. (cx, 35). 
Shell rounded, subequilateral, beaks turned forwards ; posterior 
side slightly folded; hinge-teeth 2°2, laterals elongated, distinct 
in the right valve; external ligament short, cartilage internal, 
long, oblique ; pallial sinus deep, rounded. 
SynposmyA, Recluz, 1843. 
Syn.— Abra, Leach, MSS. 
Distr.—Norway, Britain, Mediterranean, Black Sea, India. 
Fossil, 6 sp. Eocene—; Britain, France. S. alba, Wood (cx, 86). 
S. brevis, Desh. (cx, 37). 
Shell small, oval, white and shining; posterior side shortest ; 
umbones directed backwards; cartilage-process oblique; hinge- 
teeth minute or obsolete, laterals distinct ; pallial sinus wide and 
shallow. 
Animal with the mantle open, fringed ; siphons long, slender, 
diverging, anal shortest, orifices plain; foot large, tongue-shaped, 
pointed ; palpi triangular, nearly as large as the gills; branchiz 
unequal, triangular. 
The species are few, and mostly boreal, ranging from the 
laminarian zone to 180 fathoms.—Forses. They live buried in 
sand and mud, but when confined are able to creep up the sides 
of the vessel with their foot. 
Taeora, H.and A. Adams, 1854. 
Syn.—Endopleura, A. Ad. 
Distr.—4 sp. Hastern seas. T. lata, Hinds (cx, 38). 
Shell compressed, transversely oval, smooth, polished, gaping 
behind; ligament lodged in the cardinal pit; pallial sinus pro- 
found. 
A. Adams considers the species of Theora to be without 
primary teeth, which certainly is not always the case. He conse- 
quently suggests for a peculiar Chinese form with a “ primary 
tooth in front of the oblique cartilage-pit ” and ‘“ with an internal 
rib extending from the beaks obliquely towards the anterior 
side,” the name Endopleura as a subgenus. The internal rib 
may be characteristic, but this is not the case as regards the 
presence of cardinal teeth. 
The Theore live in mud and sometimes brackish water. The 
animal has a strongly compressed, linguiform foot, and two per- 
fectly separated long siphons. 
Lepromya, A. Adams, 1864. 
Distr.—2 sp. LL. cochlearis, Hinds. 
Shell thin, ventricose, beaked posteriorly ; surface of valves 
