Bulletin of the British Museum (Natural History)

Framed Prints

Framed Print of Bulletin of the British Museum (Natural History)

Bulletin of the British Museum (Natural History). OSTEOGLOSSOMORPH HYOID MUSCULATURE 45 fig. 20). Neither muscle meets the other at any point, although they are closely aligned anteriorly. The muscles originate in part from the epi- and ceratohyal, and in part from the first branchiostegal ray. In large individuals each muscle is incompletely divided, horizontally, so as to virtually form a small dorsal and larger ventral muscle (text-fig. 20). The ventral subdivision is that described above; the dorsal part originates on the epihyal and inserts on the inner face of the dentary about halfway. Bulletin of the British Museum (Natural History). OSTEOGLOSSOMORPH HYOID MUSCULATURE 45 fig. 20). Neither muscle meets the other at any point, although they are closely aligned anteriorly. The muscles originate in part from the epi- and ceratohyal, and in part from the first branchiostegal ray. In large individuals each muscle is incompletely divided, horizontally, so as to virtually form a small dorsal and larger ventral muscle (text-fig. 20). The ventral subdivision is that described above; the dorsal part originates on the epihyal and inserts on the inner face of the dentary about halfway along its length. The smallest fish examined (14-0 cm standard length) has no division, or even incipient division, in the muscle; consequently the single muscle on each side appears to have a double insertion, one anteriorly and the other laterally at about the middle of the dentary. These muscles (or muscle) correspond, in most details, to the interhyoideus of mormyrids, and are identified as such in Gymnarchns. One difference in the interhyoid of Gymnarchns is the considerable proportion of muscle originating from the first branchiostegal ray (text-fig. 20). In mormyrids the interhyoid originates exclusively from the hyoid bar, and there is complete separation between the interhyoid and the hyohyoideus. The situation in Gymnar- chns is very different. In fact, the muscle described above could well be a combined inter- and hyohyoideus. In Gymnarchns the only clearly recognizable hyohyoideus is the superior or interbranchiostegal ray portion (text-fig. 20); here it is represented by a few, well-spaced oblique fibres running between the branchiostegal rays. No distinct inferior hyohyoid can be recognized. Indeed, those fibres, which, topo-. HaB [•'iG. 20. Gymnarchns niloticits: ventral hyoid musculature. Anterior intermandibularis cut and reflected to the right; left interhyoideus reflected to the left.. Please note that these images are extracted from scanned page images th. © Book Worm

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Media ID 48217766