284 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



but are capable of considerable movement, so that they may lie almost 

 parallel to the longitudinal axis. At the base the bone forms a com- 

 plete sheath for the cartilage which supports the maxillary tentacle, 

 but this sheath is complete only for a short distance, the cartilage 

 lyino- in a groove in the posterior (inner) surface of the bone. At 

 the base are two processes, a smaller posterior dorsal and a larger 

 anterior ventral. The latter has a fascia firmly attached to it in such 

 a way that, when the anterior extremity of the palatine is pushed 

 forward it draws the same fascia, and by the tension thus produced 

 the maxilla is abducted or pushed away from the sides of the skull. 

 The bones possess no teeth. They have in relation to them the pre- 

 maxillce in front and below ; the palati/nes behind ; and the adnasals 

 on the inner side. 



3. The Palatine, (PL II., Fig. I, Pa.) 



Each palatine is a short, rod-shaped bone, extending antero-posteri- 

 orly parallel with the long axis of the skull. The anterior extrem- 

 ity abuts upon the maxilla, and the posterior lies in front and out- 

 side of No. 4, and below the antorbital process of the ectethmoid. 



4. (PL II., Figs. 1 & 4). 



This is a small almost round scale-like bone, lying behind and 

 within the posterior extremity of the palatine. It is developed in 

 the fascia of the anterior fibres of the adductor arcils palatini muscle, 

 and cannot be referred to the pterygoid series of bones. In a speci- 

 men of the very closely related Amiurtis nigricans, (LeS) Gill, it was 

 quite absent. 



5. Metapterygoid, (PL II., Fig. 1, Mpt.) 



Is an almost square bone, lying directly behind No. 4. It is flat- 

 tened and its upper posterior border is somewhat concave, aiding in 

 the formation of the notch for the passage of the trigeminus to the 

 superficial muscles. The anterior superior angle is attached by liga- 

 ment to the orbitosphenoids'. The bone articulates in front with 

 No. 4 ' behind with the hyomandibular, and below with the quad- 

 rate. 



6. The Quadrate, (PL II., Fig. 1, Qu.) 



Furnishes the articular surface for the mandible. It is triangular 

 in shape, thicker behind and below, the upper portion being squa- 

 mose. In a deep fossa, on the upper and posterior portion of the 



