FISHERY BULLETIN: VOL. 73, NO. 3 



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Figure 46.-Left subopercles of six species of Sardini, external view. a. Cybiosarda elegans, Western Australia, 422 mm 

 FL. b. Orcynopsis unicolmr, Tunisia, 645 mm FL. c. Sarda australis, New South Wales, 405 mm FL. d. Sarda chiliensis, 

 Callao, Peru, 549 mm FL. e. Gymnosarda unicolor, Amirante Islands, 713 mm FL. f . Allothunnus fallai, California, 680 

 mmFL. 



BRANCHIAL ARCH. -The branchial arch is 

 composed of the five pairs of gill arches: gill 

 filaments, gill rakers, pharyngeal tooth patches, 

 and supporting bones. The general arrangement 

 in the Sardini (Figure 49) is similar to that found 

 in other scombrids such as Thunnus (Iwai and 

 Nakamura 1964a:22, fig. 1; de Sylva 1955:21, fig. 

 40), Scomberomorus (Mago Leccia 1958:327, pi. 12), 

 and Rastrelliger (Gnanamuttu 1971:14, fig. 6). 

 Within the Sardini, the most important generic 

 and specific differences are in the number of gill 

 rakers. All of the branchial bones bear patches of 

 tiny teeth. 



Basibranchials.-The three basibranchials form 

 a chain from anterior to posterior. The first and 

 second are about the same size and considerably 

 shorter than the third. The first basibranchial is 

 covered dorsally by the broad, flattened glossohyal 

 which is dentigerous in Cybiosarda, Orcynopsis, 

 and Gymnosarda as described in the hyoid arch 

 section. 



In lateral view (Figure 50), the first 



basibranchial has an expanded anteroventral end 

 and is curved downward except in Allothunnus 

 (Figure 50f). The second basibranchial has a 

 prominent notch in the ventral margin that is ab- 

 sent in Allothunnus. The third basibranchial has 

 an expanded anterior end at its junction with the 

 second basibranchial and then tapers posteriorly. 

 A section of cartilage extends posteriorly to ar- 

 ticulate with the fourth ceratobranchial and lower 

 pharyngeal. 



Hypobranchials.-The first three arches have 

 hypobranchials which connect with the cera- 

 tobranchials. The first hypob ranch ial is attached 

 to the second basibranchial; the second and third 

 hypobranchials are attached to the third 

 basibranchial. The first two hypobranchials are 

 longer than the third. 



Ceratobranchials.-The ceratobranchials are the 

 longest bones in the branchial arch and support 

 most of the gill filaments and gill rakers. The first 

 three are morphologically similar and articulate 



568 



