Fig. 132.—A, Muco-cartilage of Lower Lip of Ammocœtes ("Mc."); "m.ph.", muscle of lower lip; "m.sm.", somatic muscle; "Cor.", laminated layer of skin. B, Degenerated Muco-cartilage of Branchial Region. "F.", fat layer; "P.", pigment; "Bl.", blood-space; "N.", somatic nerve; "m.br.", branchial muscle; "m.sm.", somatic muscle. (All references in this work to "Ammocœtes" or "Petromyzon" appear to refer to the European Brook Lamprey, now called "Lampetra planeri".)