638 J. TLAYFAIR MCMURRICn. 



ment of the maiulible^ and at the same time an enlargement of 

 the buccal cavity, whereby water for respiration is drawn in. 

 Tliese bones form consequently an important portion of the 

 respiratory pump, acting as it were the parts of handles, 

 whereby the force of the muscles is transmitted to the man- 

 dible and to the buccal cavity. The geniohyoid element 

 does not appear to ossify and in fact has disappeared. 



Extending forwards horizontally from the hyomandibular 

 almost to the extremity of the elongated snout, is the sym- 

 plectic, the cartilages of the two portions of the arch being 

 continuous. Posteriorly (fig. 11, Syui.) the bone is oval in 

 shape, and consists mainly of the original cartilaghious bar, 

 the osseous portion being small. In the anterior portion of 

 tlie orbital region, however, the latter becomes greater in pro- 

 portion to the cartilage, and the bone assumes a hammer 

 shaped appearance on section, the two heads of the hammer 

 articulating Avith a membrane bone afterwards to be described, 

 and enclosing with it a space. The handle is directed up- 

 wards towards the orbit. In the nasal region (fig. 12, Sym.) 

 the handle has extended upwards to articulate with a mem- 

 brane bone bounding the nasal cavity below, and the hammer 

 shape has entirely disappeared. Anteriorly (fig. 13, Sym.) the 

 symplectic becomes completely surrounded by the quadrate 

 (Qu.), and its cartilage becomes entirely absorbed, its position 

 being indicated by a round foramen in the section. 



The quadrate (Qu.) extends backwards to the region of the 

 nasal capsules. It then consists (fig. 12) of a small oval portion 

 lying below the symplectic. Anteriorly (fig. 13), however, it 

 enlarges and grows upwards on the outer side of that bone, and 

 finally completely encloses it as mentioned above. Tlie cartilage 

 is entirely absent from the bone posteriorly, and it is only in 

 its most anterior part that it is present. 



Lying outside the symplectic, and slightly bending round so 

 as to bound it below, there is to be seen in the orbital region a 

 membrane bone (Inf. Or.). It bounds the orbit below, and 

 corresponds to a certain extent with a bone, or a series of bones, 

 in other Teleosts, which usually receive the name of infra- 



