FISHERY BULLETIN: VOL. 73, NO. 3 



SUPRAOCCIPITAL CREST 



EPIOTIC 



PARIETAL 



EXOCCIPITAL 



FRONTAL 



PTEROTIC 



BASIOCCIPITAL 



INTERCALAR 



PROOTIC 



PARASPHENOID 



LATERAL ETHMOID 



Figure 26.-Rear view of skull of Sarda chiliensis, Callao, Peru, 571 mm FL. X's indicate the points of attachment of 



intermuscular bones. 



temporal. In Allothunnus, this protuberance 

 projects out from the posterior outline of the skull, 

 while in other bonitos this outline is smooth. Ven- 



trally, the intercalar articulates with the prootic 

 bone anteriorly and the exoccipital and pterotic 

 bones laterally (Figures 15-19). 



Figure 27. -Nasals of six species of Sardini, left external 

 view. a. Cybiosarda elegans, New South Wales, 355 mm FL. b. 

 Orcyrurpnis unicolor, Tunisia, 645 mm FL. c. Sarda chiliensis. 

 Callao, Peru, 442 mm FL. d. Sarda sarda, Florida, 333 mm FL. e. 

 Gymrwsarda unicolor, Truk Islands, 772 mm FL. f. Allothunnus 

 falUii, Tasmania, 775 mm FL. a-d drawn twice as large as e and 

 f. 



BASICRANIAL REGION.-This region con- 

 sists of the parasphenoid, basioccipital and exoc- 

 cipital bones, and forms the posteroventral base of 

 the skull. 



Parasphenoid. -Ventrally, the parasphenoid is a 

 long cross-shaped bone (Figures 15-19) which ar- 

 ticulates with the vomer anteriorly and forms the 

 ventral axis of the skull. The lateral wing of the 

 parasphenoid extends dorsolaterally along the 

 ventral ridge of the prootic bones on either side 

 and has a pointed end, which forms part of the 

 anteroventral wall of the posterior myodome. 

 Posteriorly, the parasphenoid bifurcates into two 

 lateral flanges which attach dorsally to the corres- 

 ponding posteroventral flanges of the basioccipital 

 bone and surround the posterior opening of the 

 posterior myodome. A ventrally projecting keel is 

 present along the posterior two-fifths of the 

 parasphenoid. The V-shaped joint connecting the 

 parasphenoid with the vomer anteriorly is most 



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