A buccal cavity, a pharynx, an oesophagus and an intestine are always distinguishable.
The buccal region is unarmed and not eversible.
In the Gastropoda the muscular tissue of the buccal mass is coloured red by haemoglobin.
In some Indian and Malay Engystomatids of the genera Callula and Microhyla, the tadpoles are remarkably transparent, and differ markedly in the structure of the buccal apparatus.
Parapod.ia hardly projecting; palps of prosomium forming branched gills; no pharynx or eversible buccal region; no septa in thorax, septa in abdomen regularly disposed.