Brooks — The Osteology and Arthrology of the Saddock. 183 



The third hypobranehial consists of a broad posterior part, hol- 

 lowed below, and nearly flat above, and a curved anterior process ; 

 this process bends inwards, and is connected by a ligament to its 

 fellow of the opposite side, thus arching over the cardiac aorta, 

 and a large vein, wliich lies between their processes and the 

 copulae ; they underlie the hypobranchials of the second arch. 

 The inner margins of the broad posterior part join the postero- 

 lateral edges of a diamond-shaped ossification of the copulse. Pos- 

 teriorly the bone supports the third and fourth ceratobranchials, 

 hence it may represent the third and fourth hypobranchials 

 fused. 



The epipharyngeal bones consist of three pieces, which (for 

 convenience) are referred to as a, h, and c (see PL YII., fig. 16). 

 They are all concave and irregular above, and convex and dentige- 

 rous below. They oppose the hypopharyngeal bones, and are sus- 

 pended to the skull and vertebral column by muscles. The piece 

 a is the most anterior, and its long axis runs backwards and 

 inwards; parallel to this axis it articulates with h internally; its 

 posterior angle nearly touches c; the anterior angle rises into a 

 process, which supports the first epibranchial (fig. 16, i) ; near the 

 posterior angle it supports part of the second epibranchial, which 

 forms a double condyle, to articulate with a and h. The piece b 

 is the largest, and is" roughly triangular; it articulates with c 

 postero-externally, and with a externally ; on the edge which 

 articulates with c is a ridge, 3, which is coated with cartilage, and 

 supports part of the third and fourth epibranchials, which articu- 

 late both with it and c. The piece c is a small oval bone, which 

 articulates with b, as above mentioned ; the upper surface is con- 

 cave, the hollow being filled with cartilage, which joins the ridge 

 on b, and supports the third and fourth epibranchials. 



The ossifications in the copulse consist of a diamond-shaped 

 piece of bone, ending in a long spicule in front, and a shorter one 

 behind. This bony part supports all the hypobranchials ; a slender 

 rod of cartilage underlies the front spicule, and is prolonged for- 

 wards between the superior hypohyals, forming the entoglossaL 

 From the posterior spicule a similar piece stretches backwards 

 between the ceratohyals of the fourth arch, articulating with them, 

 and is connected by ligament to the hypopharyngeal bones. This 

 is the urohyal. 



