portion it attaches to the lateral and ventral surfaces of 

 the premaxillary. Ventrally the medial surface of the 

 maxillary articulates by tough fibrous tissue with the 

 lateral surface of the posterodorsal part of the dentary, 

 while along its anteroventral edge the maxillary ar- 

 ticulates similarly with the premaxillary. 



Lower Jaw. 



Dentary. — The posterior end concave to accom- 

 modate the anterior end of the articular, which it broad- 

 ly overlies laterally but only slightly overlies medially; 

 articulates by fibrous tissue anteromedially with its op- 

 posite member, posteroventrally with the angular, and 

 posteromedially with the articular. Along the postero- 

 dorsal region of its lateral surface the dentary ar- 

 ticulates by tough fibrous tissue with the medial surface 

 of the ventral portion of the maxillary. Seven to eight 

 bluntly conical teeth, decreasing in size laterally, are 

 borne in deep sockets along the anterior edge of the den- 

 tary. Behind and internal to this outer row of teeth there 

 is usually a single conical tooth, about half the size of the 

 largest tooth in the outer series, but several such inner 

 teeth may be present on each dentary. The teeth of the 

 outer series are replaced by new ones developing in new 

 sockets just below and external to the sockets of the outer 

 row of teeth, in the same manner as described for the 

 premaxillary. 



Articular. — More or less triangular in shape; 

 cartilage filled at its anterior edge, where it is con- 

 tinuous with the remains of Meckel's cartilage; ar- 

 ticulates by fibrous tissue dorsally, ventrally, and 

 laterally with the broadly overlying dentary, postero- 

 ventrally with the angular, and posteriorly at the groove 

 on its posterior edge with the knob at the anterior end of 

 the quadrate. The sesamoid articular is a small ossifica- 

 tion held by fibrous tissue to the region of juncture of 

 Meckel's cartilage and the anteromedial surface of the 

 articular. 



Angular. — Small; articulates by tough fibrous tis- 

 sue with the dentary and articular. Posteriorly the 

 angular connects by ligament to the anterior end of the 

 interoperculum. 



BRANCHIAL APPARATUS. 



and with the ceratohyal, while they articulate by fibrous 

 tissue anteromedially with their opposite members, and 

 in the case of the dorsal hypohyal with the region of ar- 

 ticulation between the basihyal and first basibranchial. 

 The ventral edge of the ventral hypohyal articulates by 

 fibrous tissue with the urohyal. 



Ceratohyal. — Large, somewhat expanded pos- 

 teriorly; cartilage filled at its anterior and posterior 

 edges; articulates through cartilage anteriorly with both 

 of the hypohyals and posteriorly with the epihyal. The 

 six branchiostegal rays articulate by fibrous tissue with 

 the ceratohyal; the first two rays to about the middle of 

 the ventral edge and the last four rays to the lateral sur- 

 face of its posteroventral region. 



EpihyaL — Large; cartilage filled at its anterior and 

 ventral edges; articulates through cartilage anteriorly 

 with the ceratohyal and posterodorsally by fibrous tis- 

 sue with the interhyal. 



Interhyal. — Short, columnar; cartilage filled at its 

 dorsal and ventral edges; articulates by fibrous tissue 

 ventrally with the epihyal and dorsally with the car- 

 tilaginous plate between the symplectic and hyoman- 

 dibular. 



Branchiostegal rays. — Six in number, increasing in 

 length posteriorly in the series; the first ray somewhat 

 flattened or laterally compressed, the succeeding rays 

 less compressed so that the sixth ray is rodlike; ar- 

 ticulate by fibrous tissue with the ceratohyal as de- 

 scribed above. 



Urohyal. — Thick at its dorsal and anterior edges, 

 otherwise very thin; articulates by fibrous tissue with the 

 ventromedial surfaces of the ventral hypohyals. 



Branchial Arches.— All the elements are cartilage 

 filled at their edges of articulation with the other ele- 

 ments of the series, and the articulations are usually 

 through cartilage and fibrous tissue. The branchial 

 arches are composed of three basibranchials, three pairs 

 of hypobranchials, five pairs of ceratobranchials, four 

 pairs of epibranchials, and four pairs of pharyngobran- 

 chials. Four gills are present, with a slit between the 

 fourth arch and the lower pharyngeal. 



Hyoid Arch, Branchiostegal Rays, and Urohyal. 



Basihyal. — Elongate; slightly expanded laterally 

 at posterior end; cartilage filled at posterior end; ar- 

 ticulates by fibrous tissue posteriorly with the first 

 basibranchial and laterally with the dorsal hypohyals. 



Hypohyals. —Both hypohyal elements well de- 

 veloped; dorsal hypohyal cartilage filled at its ventral 

 and posterior edges, the ventral hypohyal cartilage filled 

 at its dorsal and posterior edges. The dorsal and ventral 

 hypohyals articulate through cartilage with one another 



First Arch. — Basi-, hypo-, cerato-, epi-, and 

 pharyngobranchial elements present. First basibranchial 

 short, laterally compressed in the middle of its length; 

 displaced forward so that it articulates posteriorly main- 

 ly with the second basibranchial and only secondarily 

 posterolaterally with the first hypobranchials, while an- 

 teriorly it articulates with the basihyal. First hypo- 

 branchial the largest of the hypobranchial elements, 

 which decrease in size posteriorly in the series; ar- 

 ticulates mainly with the anterior half of the lateral sur- 

 face of the second basibranchial, and to a lesser extent 

 along its extreme anteroventral edge with the first basi- 



