244 GINGLYMACONCHA. 
CLASSIS V. GINGLYMACONCHA. 
Testacea bivalvia, ductorum. 
Acephala, Cuvier. 
Mollusca conchifera, Lamarck. 
The body is covered by two shells, which are opened by an 
internal or external hinge-formed elastic ligament, and are closed 
by one, two or more muscles and elastic tendons: the hinge is 
furnished with a few, many or no teeth. 
The head is concealed ; it consists of a simple round aperture 
generally furnished with two bilobate lips; it has neither eyes, 
tentacles nor maxillee (or jaws). 
The two branchize, which are thin and reticulated, are placed 
at the sides of the abdomen, and are covered by lobes of the 
mantle. 
The mantle covers the body ; its two thin lobes protect the 
branchize, and it is generally produced posteriorly into two elas- 
tic respiratory tubes. 
The foot is situated anteriorly, arising from the extremity of 
the abdomen ; it passes in and out between the anterior junc- 
tion of the mantle. 
The sex is androgynous, ovo-viviparous. 
General Observations on this Class. 
The animals of this class have no apparent head, but merely 
a mouth with a rounded aperture, and two bilobate lips con- 
cealed at the bottom of the replication of the mantle: it has 
no maxillee or jaws, no tongue, tentacula or eyes; it feeds on 
the animalcules which are brought in with the water which 
serves for respiration ; the cesophagus is extremely short ; it is 
dilated into one, and sometimes into two stomachs; the intes- 
tines vary much in length and diameter; they surround the 
liver, which is very large; the bile passes into them generally 
by many small apertures. 
