no ALUS. [Vol. XVIII. 



mesial process of the bone after that process had been so devel- 

 oped. As the hind edge of the bod}^ of the bone lies approximately 

 in the line of the superficial edge of the second septum, the bone 

 thus only covers, approximately, one muscle segment, the second 

 segment of the trunk. 



The Supraclavicular has the general shape shown in Fig. 

 27, but it is often much more diamond-shaped than there shown. 

 The antero-ventral half of the diamond is always considerably 

 narrower and thicker than the dorso-posterior half, and a strong 

 ridge crosses the bone from angle to angle between the two por- 

 tions. The postero- ventral half of the bone lies superficial to, and 

 is bound by fibrous or ligamentous tissue to, the dorsal end of the 

 clavicle. The bone ends postero-ventrally in a sharp point, which, 

 when in position, lies slightly dorsal to an eminence on the antero- 

 lateral edge of the clavicle. The antero-dorsal end of the bone is 

 usually blunt, but may have a short process directed somewhat for- 

 ward. The dorsal third or half of the bone is overlapped exter- 

 nally by the hind end of the suprascapular, the anterior edge of 

 the supraclavicular fitting into the space between the internal sur- 

 face of the body of the suprascapular and the short process that 

 projects laterally and ventrally from the base of the leg of that 

 bone. 



On the inner surface of the posterior half of the supraclavicular, 

 immediately dorsal to the dorsal edge of the clavicle, and some- 

 times also partly on the latter bone, a large ligament coming from 

 the hind end of the lateral surface of the basioccipital has its inser- 

 tion. This ligament, at its distal end, usually separates into three 

 parts, one of which turns upward and one downward immediately 

 posterior to the thickened central part of the supraclavicular, the 

 third one running backward toward the posterior corner of the 

 bone. The bone is traversed, near its dorso-posterior edge, by the 

 hind end of the main infraorbital lateral canal. 



The Infraorbital Chain of bones is a series of thin and deli- 

 cate bones, usually ten or twelve in number. The anterior bone of 

 the series is much larger and stouter than the others, and cor- 

 responds, in general position, to the lachrymal of other fishes. 

 The hind edges of all the bones, the lachrymal included, overlap, 

 or are overlapped by, the anterior edges of numerous scale-like 



