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organs. The ventro-posterior corner of the bone is prolonged into a short process which has articular 

 surfaces for articulation with the pontinal. 



The pontinal is a small and somewhat elongated bone, which extends frorn the second infra- 

 orbital into a reentrant angle on the anterior edge of the preopercular, articulating with and being 

 firmly bound to each of these two bones. It does not lodge any part of the latero-sensorv canal, 

 and is aecordingly either an independent dermal ossicle or a detached portion of the seeond infra- 

 orbital bone. 



The third infraorbital bone bears, along the internal surface of its orbital margin, a large thin 

 projecting plate of bone which forms about one half of the floor and a corresponding part of the posterior 

 wall of the orbit. The central portion of this orbital shelf is supported by a bracing web of bone 

 which arises from the internal surface of this bone and is continued beyond it onto the internal surface 

 of the second infraorbital bone, near its hind edge. From the internal surfaces of the adjoining edges 

 of these two infraorbital bones, immediately anterior to the bracing web, a strong ligament arises, 

 and running forward has its insertion on the ventral surface of the dorsal limb of the dentary. The 

 anterior end of the orbital shelf projects forward beyond the anterior edge of the body of the bone, 

 along the inner surface of the first infraorbital, and eomes into sutural contact with, and is firmly 

 bound to. the hind edge of the dorsal end of the brace-like articular process of the latter bone. The 

 bone is traversed by the main infraorbital latero-sensory canal and lodges three organs of the line. 



The fourth infraorbital is a small bone, postorbital in position, that is in contact ventrally 

 with the third infraorbital and dorsally with the postfrontal. It transmits the latero-sensory canal 

 from the former to the latter bone, lodging one organ of the line. 



The first and third infraorbital bones are the preorbital and fourth suborWtal, respectively, 

 of Gill's descriptions; and these two bones and the second infraorbital, together, form the first sub- 

 orbital of Cuvier and Valenciennes' descriptions. The second suborbital of Cuvier and Valenciennes 

 is the third suborbital, or pontinal of Gill's descriptions, but this bone, not being traversed by the 

 infraorbital canal, would seem not to properly be an independent element of the infraorbital series. 



3. SUSPENSORIAL APPARATUS AND MANDIBLE. 



The bones that form the hyomandibulo-palato-quadrate apparatus are firmly united to form 

 two pieces with a flexible Joint between them. The posterior and much larger piece is formed by 

 the preopercular, hyomandibular, symplectic, quadrate and metapterygoid; and the anterior piece 

 by the palatine, the ectopterygoid and the entopterygoid. The flexible Joint between the two pieces 

 is nearly transverse to the axis of the body of the fish, and permits that extensive lateral motion 

 of the hind end of the apparatus that easily places the large preopercular spine at an angle of more 

 than 45° to the axis of the bodv. 



The PREOPERCULAR has a horizontal limb, which terminates in the long and well known 

 spine, and a vertical limb which extends antero-dorsally at an angle of about 75° to the horizontal 

 limb. In the angle between the two limbs there is an articular facet, and immediately dorsal to this 

 facet an articular eminence, both of which give articulation to corresponding surfaces on the hind 

 end of the pontinal. The angle between the two limbs is spanned by a large web of bone which 

 arises from the deeper layers of the preopercular; and, external to this web, on either limb of the 

 bone, between the web and the outer surface of the thick, related limb, there is a large V-shaped 



