Brooks — The Osteology and Arthrology of the Haddock. 181 



bone, is connected to it above and to the two hypohyals below ;. 

 the union to them is chiefly by the mediation of cartilage. The 

 bone is flattened from side to side, and curved, so as to present a 

 slight concavity upwards and forwards ; part of the bone, thinner 

 than the rest, projects downwards and slightly outwards, and is 

 marked with notch-like depressions on the -outer surface above, 

 and on the inner below, for the branohiostegal rays ; the latter are 

 slender, curved, flattened rods of bone, with a sharp edge on the 

 middle of their convex border :" they decrease in size from above 

 downwards ; four of them articulate with the outside, and three 

 with the inside of the ceratohyal ; their direction is upwards, back- 

 wards, and slightly outwards ; they support the membranous inner 

 gill- cover, by which they are connected to the inter- and sub- 

 operculum. 



The two hypohyals, usually called inner and outer, may, from 

 their position in tlie haddock, be more appropriately called superior 

 and inferior. The inferior is slightly anterior to the other ; they 

 are both small pyramidal bones, the bases of the pyramids being 

 turned outwards ; there is a considerable amount of cartilage 

 between them and the ceratohyal, and in this, on the outside, is 

 seen the opening of a canal, which passes downwards and inwards, 

 its inner opening being bounded by the two lower bones, which are 

 notched in this situation. This canal transmits a vessel, conveying 

 arterial blood from tlie first branchial arch to the pseudobranchia. 



The superior hypohyals are the smaller ; their apices articulate 

 with the entoglossal cartilage, which keeps them apart. A ridge 

 running along the inner side of the anterior border joins a similar 

 ridge on the inferior hypohyal. 



The inferior hypohyals articulate with each other by their 

 apices, which are anterior and internal, and by the anterior 

 half of a ridge on their inner surface behind this ; they form the 

 chief support of the tongue* 



The basibranchiostegal (PI. VII., fig. lQ,'d) is a thin, irregularly 

 quadrilateral plate of bone, the upper border being the thickest, 

 slightly grooved, and running into a distinct notch, where it meets 

 the anterior border : from the margins of this notch a pair of strong 

 ligaments pass to the apices of the inferior hypohyals : behind this 

 the bone is connected by ligaments to the superier hypohyals. 

 The anterior border is sharp and distinct, the posterior and inferior 



