类主要利用鳃呼吸,皮肤和鳔是辅助呼吸器官。鳃基部是鳃弓,每一鳃弓发出两列鳃丝,鳃丝紧密排列成十分整齐的梳状及薄片状,称鳃片(鳃瓣),鳃丝内有约为鳃丝全长2/3的鳃丝软骨。每根鳃丝两侧又发出许多纤细的叶片状突出,称为鳃小片。在鳃弓软骨的下方有二支血管,腹侧一支为入鳃动 The main use of class gills breathing, skin and bladder is auxiliary respiratory organs. The gill base is the gill arch, each gill arch issued two rows of gill filaments, gill filaments closely arranged in a very neat comb and flake, said the gill (gill flap), gill filaments about gill filaments full length 2 / 3 gill filaments cartilage. Gill filaments on both sides of each issued a number of slender leaf-shaped prominent, known as gills. Under the gill arch cartilage has two blood vessels, one for the ventral gill into motion