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dentary lodges four organs of the sensory line and the articular, one. Primary tubes leave the canal 

 at either end of the angular, and four tubes leave it as it traverses the dentary, one of these tubes 

 being the anterior terminal tube of the line. 



The dentary has the usual dorsal and ventral limbs, separated by a deep V-shaped reentrant 

 angle. The dorsal edge of the dorsal limb is lined its füll length with villiform teeth. Immediately 

 ventral to this edge, on the outer surface of the bone, and at about the middle of its length, there 

 is a large and deep depression which lodges and gives insertion to the base of a tapering gristly 

 structure which projects posteriorly and forms the core of the mandibular labial fold. This gristly, 

 semi-cartilaginous structure is attached, at its hind end, by dermal tissues to the inner surface of 

 the hind end of the maxillary, and would seem to be the homologue of the labial cartilage of Swinner- 

 ton's descriptions of Gasterosteus. 



The angular is a small bone which forms the postero-ventral corner of the mandible. Its dorsal 

 end is united by synchondrosis with the articular, immediately ventral to the articular facet for 

 the quadrate, a small interspace of cartilage here being visible on the inner surface of the mandible. 

 The angular gives insertion to a short but strong ligament which has its insertion on the ventral end 

 of the interopercular, and also gives insertion to certain of the ligamentous articular tissues that bind 

 the mandible to the quadrate. There is, as in Scomber, no evident ligamentum mandibulo-hyoideum. 



The articular has a stout coronoid process, the base of which forms the anterior portion of 

 the articular facet for the quadrate. The dorsal end of the process lies slightly postero-ventral to the 

 hind end of the dorsal limb of the dentary, and the two bones are here connected by a pad-like struc- 

 ture of tough fibrous tissue which extends forward a short distance along the lateral and dorsal sur- 

 faces of the hind end of the dorsal limb of the dentary. This päd forms, in the recent state, a 

 pronounced feature of the mandible, and the inner surface of the maxillary slides against it as the 

 mouth is opened and closed. The maxillo-mandibular ligament, as already described, runs across 

 the external surface of this päd of tissue, with apparent interchange of fibers, and has its attachment 

 to the external surface of the base of the coronoid process and the adjoining portions of the articular. 

 On the hind edge of the articular a stout curved process, projecting dorsally, forms the posterior 

 half of the articular facet for the quadrate. The dorsal end of this process gives insertion to a short 

 stout ligament which extends anteriorly and has its origin on the adjacent lateral edge of the artic- 

 ular head of the quadrate. The mesial or postero-mesial surface of the process is smooth and slightly 

 convex, is covered with a thin layer of fibrous or fibro-cartilaginous tissue, and, when the mouth 

 is opened and shut, slides upon a part of the hind edge of the quadrate immediately dorso-posterior 

 to the articular head of that bone; the outer, dorso-posterior end of the process finally abutting 

 against a part of the quadrate, and so limiting the opening movement of the mandible. This sliding 

 articulation of this process of the articular is with the posterior process of the quadrate, and not 

 with the body of that bone, and manifestly recalls the mandibulo-symplectic articulation of Anna, 

 to which reference was made when describing the quadrate. In Scomber a similar sliding articulation 

 doubtless exists, but, when describing that fish ('03, p. 157) I did not recognize it, or its probable 

 homology. 



On the internal surface of the articular, the hind end of MeckePs cartilage is continued back- 

 ward, for a short distance, as a bony ridge which presents the appearance of a posterior and ossified 

 continuation of that cartilage. On the dorsal surface of this ridge, and partly immediately anterior 

 to it, the tendon of the deeper part of the adductor mandibular has its insertion. 



