386 H. B. POLLARD, 



tunnels, being separated by a thick iuternasal septum and roofed over 

 by the bridge of cartilage, which extends from the anterosuperior 

 orbital region to the rostral region. Between the antorbital process 

 and the base of the rostral region lies the extensive floor of the nasal 

 cavity. The shape of the rostral region is best shown by the figure 

 (Fig. 3). 



The hyomandibular {H.M.) articulates, as above mentioned, with 

 the pterotic region of the auditory capsule. Its upper portion is in 

 the form of an inverted triangle, the articulation being the base of 

 the triangle. At the apex of this triangular part there is a notch in 

 front for the hyomandibular nerve, while behind is attached the oper- 

 cular cartilage which bears the operculum. 



From this level the hyomandibular cartilage broadens downwards 

 and forwards to the quadrate and symplectic regions. At the poste- 

 rior ventral angle, that is in the symplectic region, is attached the 

 stylohyal, while at the most ventral, or quadrate region, is situated 

 the articulation for the lower jaw. Inwardly and forwards, the qua- 

 drate is prolonged into the small pterygoid process, which in Silurus 

 is attached by a ligament to the vomer. 



The prepalatine piece articulates with the antorbital process. It 

 is an irregularly shaped block of cartilage. In some specimens there 

 may be found at its anterior edge accessory nodules of cartilage. 

 Externally it bears the procartilaginous axis of the maxillary barbel 

 {Mx. t), which proceeds out at a right angle for a short distance, 

 then turning backwards. The prepalatine piece has no connection with 

 the pterygoid process. 



In front of the rostrum is a small triangular block {Pmx.p.) 

 representing somewhat schematically the premaxillary block of pro- 

 cartilage. 



The Meckelian cartilage {Mck.) passes horizontally forward from 

 its articulation with the quadrate. An angular process, however, 

 passes downwards and backwards from the articulation. At some 

 little distance forward, the coronoid process is given off. The coro- 

 uoid process {Proc. cor.) projects vertically u])ward and bears the 

 procartilaginous, cylindrical, horizontally placed coronoid piece {Cor.p.)^ 

 which reaches forward to the level of the prepalatine piece, its end, 

 in fact, approaching the ujaxillary tentacle. 



Directly below the coronoid process lies the proximal portion of 

 the submandibular tentacle {Suhm. t.), and, some little distance in 

 front of this, in seen the corresponding part of the mental tentacle 



