It is the approximate equality in the size of the anterior and posterior adductor muscles which led to the name Isomya for the group to which Anodonta belongs.
The early larva of Anodonta is not unlike the trochosphere of other Lamellibranchs, but the mouth is wanting.
Aa, ae, af, ag, ah, ak, al, am, an, ap, aq, ar, as, at, au, av, aw, ax, ay, az, bb, In Anodonta these pallial tentacles are confined to a small area surrounding the inferior siphonal notch (fig.
The actual condition in Anodonta at the region where the gills begin anteriorly is shown in fig.
The gonads of Anodonta are placed in distinct male and female individuals.
The labial tentacles or palps of Anodonta (n, o in fig.
The gill-plates have a structure very different from that of the labial tentacles, and one which in Anodonta is singularly complicated as compared with the condition presented by these organs in some other Lamellibranchs, and with what must have been their original condition in the ancestors of the whole series of living Lamellibranchia.
The sense-organs of Anodonta other than the osphradia consist of a pair of otocysts attached to the pedal ganglia (fig.
In Anodonta the blood is driven by the ventricle through the arteries into vessel-like spaces.
Unio differs in no important point from Anodonta in internal structure.