. Bulletin of the British Museum (Natural History) Zoology. Fig. 6 3rd & 4th pharyngobranchials and tooth- plates of Mugil cephalus (PA 271186T, mm SL) in A, dorsal and B, lateral views. In B, the 4th toothplate has been separated from the 3rd pharyngobranchial to show detail of opposing surfaces. For clarity, the 3rd toothplate has been removed from its supporting bone and only a few distal teeth are shown on toothplate 4. Scale = mm. eb4. Fig. 7 Upper gill-arch elements of Liza ramada (PA 17986T, mm SL). Gill-filaments are shown extending from the 2nd cerato- branchial proc
. Bulletin of the British Museum (Natural History) Zoology. Fig. 6 3rd & 4th pharyngobranchials and tooth- plates of Mugil cephalus (PA 271186T, mm SL) in A, dorsal and B, lateral views. In B, the 4th toothplate has been separated from the 3rd pharyngobranchial to show detail of opposing surfaces. For clarity, the 3rd toothplate has been removed from its supporting bone and only a few distal teeth are shown on toothplate 4. Scale = mm. eb4. Fig. 7 Upper gill-arch elements of Liza ramada (PA 17986T, mm SL). Gill-filaments are shown extending from the 2nd cerato- branchial process to above the uncinate process of the 2nd epibranchial. Scale = mm. suitable for filtering the current is then forced over the sulcus border and filtered across the denticulate area. Small corruga- tions along the border possibly aid in channelling and altering the nature of the flow of the current as it is ejected from the sulcus. The mechanism of ejection is most likely achieved through elevation of the pharyngobranchial unit by the levator internus 2, an action which might also displace the anterior fat body outwards, thus sealing the sulcus dorsally. According to Capanna et al. (1974) the particle-laden current passes between the denticulate area and the intermeshing rakers which prevent the passage of coarser material. The structure of the PBO indicates to us that it may be able to regulate its filtering capacity by adjusting the degree of separation between the denticulate area distal-type teeth and the gill-rakers. The larger distal-type teeth along the sulcus margin and lateral face of the denticulate area presumably serve to entrap the coarser material as do the anteromedial proximal-type teeth. Transport of the particulate matter to the oesophagus is possibly via streams of mucus emmanating from the valve area (Capanna et al., 1974), Ojha & Mishra, (1987), report mucous gland openings at the base of the gill-rakers in Rhinomugit). Observations (eg., Giinthe
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