MOLLUSCA. SIPHONIDA, 
409 
A A. Shape various. 
a. Ligament internal. 
b. Inequivalve. CoRuuLADiE. 
Corbula. 
bb. Equivalve. Mactrad^e. 
c. Ligament simple. 
d. Lateral teeth. 
Mactra. . 
Goodallia. 
Lepton. 
Kellia. 
c?(?. No lateral teeth. 
Loripes. 
Ervillia. 
c c. A subsidiary external ligament. 
Amphidesma. 
a a. Ligament external. 
b. Two primary teeth, at most, on the same valve. 
pJiaces of Lamark.) 
c. Ligament at the shortest side, being the poste- 
rior one abbreviated. Donacid^. 
Donax. 
Capsa. 
Tellina. 
c c. Ligament at the longest side, 
d No lateral teeth. 
Psammobia. 
Astarte. 
d d. Lateral teeth. 
Lucina. 
Myrtea. 
b b. Three teeth, at least, on the same valve ; the other 
with an equal number, or less. {Conques of Lamark.) 
c. Marine. VeneridoE. 
Cyprina. 
Cytherea. 
Venus. 
Venerupis. 
c. c. Fluviatile. Cycladje. 
Cyclas, 
Cyrena. 
(Galateola.) 
IV. Cloak closed ventrally ; the anteal opening small, and not 
exposing the mouth or gills, and serving as a passage for 
the foot ; posterior openings tubular. 
A. Lodged at the extremity of a calcareous tube with which 
it is more or less irdimately connected. Teredinid®. 
Teredo. 
Xylophaga. 
Fistulana. 
ClavageJla, 
