Otic Region. 



Pterotic. — Cartilage filled along all of its edges of 

 articulation with the other cranial bones; articulates 

 through cartilage and interdigitation dorsally with the 

 epiotic, posteriorly with the exoccipital, ventromedially 

 on the ventral surface of the skull with the basioccipital 

 and parasphenoid, anterolaterally with the sphenotic, 

 laterally through extensive interdigitation with the 

 posttemporal which overlies a portion of its lateral 

 surface, and anteroraedially in the region of the orbit 

 by interdigitation with the prootic. The anteroventral 

 region of the pterotic is prolonged ventrally as a shaft - 

 like projection overlying and extending ventral to the 

 posterodorsal end of the hyomandibular, to which it 

 articulates by fibrous tissue. Just anteromedial to its 

 ventral shaft the pterotic bears a deep depression which 

 continues over the prootic and to which depression the 

 dorsal head of the hyomandibular is held by fibrous tis- 



Sphenotic. —Cartilage filled along all of its edges of 

 articulation with the other cranial bones except for its 

 anteroventral prong; articulates in the orbit through car- 

 tilage and interdigitation anteromedially with the ptero- 

 sphenoid, prootic, and pterotic; articulates antero- 

 laterally by extensive interdigitation with the frontal, 

 posterodorsally through cartilage and slight inter- 

 digitation with the epiotic, and posteroventrally with the 

 pterotic. 



Epiotic. — Cartilage filled along all of its edges of 

 articulation with the other cranial bones; articulates dor- 

 somedially by extensive interdigitation with the over- 

 lying basal pterygiophore of the spiny dorsal fin. Below 

 this articulation with the basal pterygiophore the dor- 

 somedial edge of the epiotic articulates through cartilage 

 and interdigitation with its opposite member in the 

 midline. Anteriorly the epiotic articulates through 

 cartilage and interdigitation dorsally with a short 

 portion of the posterior edge of the supraoccipital and 

 through extensive interdigitation along most of its 

 anterior edge with the frontal, while anteroventrally 

 it articulates through cartilage and interdigitation 

 with the posterodorsal edge of the sphenotic. Ventrally 

 the epiotic articulates through cartilage and inter- 

 digitation with the pterotic and exoccipital, while the 

 posterolateral surface of the lower half of the epiotic 

 is broadly overlain and articulates by interdigitation 

 with the bifid neural spine of the first abdominal 

 vertebra. 



Prootic. — Cartilage filled along all of its edges of 

 articulation with the other cranial bones, except antero- 

 medially; articulates by interdigitation medially with 

 the lateral surface of the parasphenoid, anteromedially 

 with the ascending fork of the parasphenoid, through 

 cartilage and interdigitation anterodorsally with the 

 pterosphenoid, anterolaterally with the sphenotic, and 

 posteriorly with the pterotic. A deep concavity on the 



ventral surface of the prootic articulates by fibrous tissue 

 with the anterior half of the dorsal head of the hyoman- 

 dibular. The medial edges of the prootics form the lateral 

 walls of the myodome, while medially directed shelves 

 from the medial edges of the prootics meet in the midline 

 and articulate through cartilage and fibrous tissue with 

 one another to form the dorsal roof of the myodome. The 

 anterior edge of the myodome is formed by the prootics, 

 except ventrally, where it is formed by the para- 

 sphenoid. The anterior end of the prootic is prolonged 

 anteriorly as a subocular shelf which serves for muscle at- 

 tachment. 



Orbital Region. 



Frontal. — Widest posteriorly, tapering to a point 

 anteriorly; its lateral edge above the orbit only slightly 

 upraised and thickened; articulates by interdigitation 

 posteromedially with the flattened posterior portion of 

 the supraoccipital, which it slightly overlies, posteriorly 

 with the epiotic, and posteroventrally with the sphenotic. 

 Posteriorly in the rear of the orbit it articulates by fibrous 

 tissue with the pterosphenoid and by interdigitation with 

 the sphenotic. Medially above the orbit the frontal 

 slightly overlies and articulates by fibrous tissue and 

 slight interdigitation with the ventrolateral edge of the 

 anterior extension of the supraoccipital, just posterior to 

 which the frontal is broadly overlain and articulates by 

 extensive interdigitation with the laterally expanded 

 middle region of the basal pterygiophore of the spiny dor- 

 sal fin. The frontal interdigitates anteriorly with the eth- 

 moid, whose posterodorsal surface it broadly overlies, 

 while laterally at the front of the orbit the frontal articu- 

 lates by interdigitation with the dorsolateral surface of 

 the prefrontal. On its ventral surface, the medial edges of 

 the frontals are separated by the cartilaginous mass 

 which is continuous anteriorly with the remains of the 

 ethmoid cartilage. 



Prefrontal. — Expanded dorsolaterally; 

 filled along its medial edge below the frontal; articu- 

 lates by interdigitation dorsomedially with the frontal, 

 while ventromedially it is continuous with the ethmoid 

 cartilage lying between it and its opposite member and 

 the posterior end of the ethmoid. 



Parasphenoid. — Elongate, expanded laterally only 

 posteriorly in the region below the rear of the orbit; ven- 

 trally expanded into a thin keel in the region below and 

 just anterior to the orbit. The bifurcate posterior end of 

 the parasphenoid broadly overlies the ventral surface of 

 the basioccipital in the region of the deep concave groove 

 in the latter, roofing over in this region the channel 

 leading into the myodome. Articulates posteriorly by in- 

 terdigitation with the basioccipital, pterotics, and 

 prootics. Under the posterior region of the orbit the para- 

 sphenoid possesses a pair of short, slightly forked, dorso- 

 lateral projections which interdigitate with the prootics 

 and form the anterior edge of the ventral region of the 

 myodome. Anterior to the orbit the dorsal surface of the 



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