~ 153 — 



surface of the third bone of the infraorbital series. The anterior Prolongation of the f lange rests 

 upon and is firmly bound to the internal surface of the ventral liinb of the second infraorbital bone. 

 The posterior process of the quadrate occupies the anterior half only of the ventral limb of the angnlar 

 groove on the preopercular, and the articular head of the bone projects beyond the anterior end of 

 the preopercular and is there exposed on the external surface of the apparatus in an angular notch 

 in the ventro-anterior Corner of the preopercular. On the internal surface of the (juadrate, there is 

 a shallow symplectic groove. 



The .METAPTERYGOID has a long and slender dorso-posterior process, the dorsal end of 

 which closely approaches and is bound by tissue to a thin web of bone on the anterior edge of the liyo- 

 mandibular; this process thus being the internal f lange on the hind edge of the bone. At the 

 base of the process there is a slightly developed external flange, the hind edges of both flanges being 

 widely separated froni the anterior edge of the hyomandibular. In the V-shaped space between 

 the two flanges a portion of the levator arcus palatini has its insertion. The ventro-anterior edge 

 of the bone is everywhere separated from the quadrate by a narrow line of cartilage, the posterior 

 Corner of this edge of the bone being in contact with the symplectic. 



The E.XTOPTERYGOID is a small, thin plate of bone which lies in the membrane that Covers 

 the ventral surface of the adductor arcus palatini muscle. Its ventral edge rests against the inner 

 surface of the narrow band of cartilage that lies between the quadrate and metapterygoid, usually 

 extending forward slightly beyond that cartilage onto the inner surface of the ectopterygoid. Its 

 hind edge overlaps slightly the inner surface of the metapterygoid. 



The ECTOPTERYGOID is a stout bone, with the usual dorsal and ventral limbs lying at an 

 angle to each other. The two limbs of the bone form a thin plate, which is completely ankylosed, 

 at the angle between the two limbs, with a plate of bone which is certainly of separate origin, and 

 which has been already referred to as the dermo-ectopterygoid. The ventral limb of the bone has 

 the usual position along the internal surface of the anterior edge of the c|uadrate, the dorsal limb 

 lying along the ventral and outer surfaces of the hind end of the palatine, and also along the same 

 surfaces of the jjalatine cartilage. 



The DERMO-ECTOPTERYGOID lies on the external surface of the thin plate formed by 

 the two limbs of the membrane-ectopterygoid, and extends from the angle between the two limbs 

 of that bone forward along the dorsal limb. It projects dorsally beyond the membrane-ectopterygoid, 

 along the lateral surface of the enlarged posterior portion of the palatine cartilage, and then beyond 

 that cartilage, there forming an important angle in the apparatus. The ectal surface of the bone 

 is presented dorso-laterally, and the posterior half of this surface lies against and is firmly bound 

 to the inner surface of the antero-dorsal corner of the third infraorbital bone. A small anterior portion 

 of the plate lies against but is nmch less firmly bound to the inner surface of the hind end of the 

 dorsal limb of the second infraorbital bone. Between these two surfaces of contact with the infraorbital 

 bones, the outer surface of the plate is granulated and comes to the level of and forms part of the 

 outer surface of the bony cuirass of the cheek. The dorsal edge of the plate is presented dorso-mesially, 

 and its thick j)o.sterior portion is grooved, the groove articulating with the articular ridge near the 

 hind end of the lateral edge of the ectethmoid. Anterior to this groove the dorsal edge of the plate 

 is thin, and lies against the lateral surface of the rod of palatine cartilage, the latter cartilage not 

 Coming into articular relations with the ectethmoid. On this thin portion of the dorsal edge of the 



Zoologien. Heft 57. 20 



