326 



KAMAKICHI ELSmXODTE: 



bone is the largest operculax bone, broadest at the middle, and tapering 

 gradually and neai'ly equally towards both extremities. In the Cybiidae 

 the horizontal limb is wide near the dorsal end. In the genus Cybium the 

 preopercle is very broad at the lower postärior angle. In the Tliunnidae the 

 horizontal limb is well developed ; but smaller than the vertical. In the 

 KatBuwonidse the horizontal limb is better developed than the vertical, and 

 both limbs taper nearly equally towards the extremities. The posterior and 

 venti'al margins of the opercular bones are attenuated and roU inward when 

 dried. 



Hyoid Arch. 



The glossohyal is a small median bone, embedded in the substance of 

 the tongue, with a narrow cartilage at the broad anterior end. In the 

 Scombridfe the bone is especially snuiU, and more or less spatulate. In 

 the Cybiidaa the bone is generally rod-hke, thick at the proximal part ; but in 

 Sarda orientalis it is spatulate. In Qymnosarda nvda the glossohyal is nearly 

 covered from both sides with the inner edge of paired semicircular dentigerous 

 ossicles. The front mai'gin of the glossohyal is neai'ly straight in the 

 Plecostei. In the Thunnidte the glossohyal is spatulate, shghtly concave above 

 and below, and constricted at the posterior end. In the Katsuwonidae the 

 bone is also spatulate, slightly concave in the cross-section. 



The hypohyal forms the symphysis with its fellow of the other side 



<5a 



Fig. E. External view o£ the hyoid arch. 1, llasirdliger chrysozonus ; 2, Scmiber 

 japoniats; 3, AcnnthocyUum solandri; i, Cybium mpltonium; b, Sarda orienlcUls ; 6, Qymnosarda 

 7iuda ; 7, Neothunnus macropterus ; 8, Katsuicorais pelamis. 



