462 HENRY C. TRACY 



of the wing joins the orbitosphenoid and ahsphenoid. The 

 distal end of this process flattens to form a thin lamella of bone 

 which fits closely over a part of the adjacerjt surfaces of the 

 pterotic and sphenotic bones on the lateral face of the skull. 

 By bridging over the interval between these bones it helps to 

 form the lateral wall of the lateral recess. 



The lateral wing of the frontal bone serves chiefly as a bony 

 sheath of the supra-orbital canal of the lateral line system. 

 In the distal third of the wing, the inner wall of the bony sheath 

 is deficient, so that here, at its origin, the supra-orbital canal 

 is neither on the surface nor enclosed in a bony sheath, but 

 lies in the lateral- recess of the cranium (fig. 9, LLC). Two 

 large foramina in the extreme distal end of the bone give passage 

 to the infra-orbital and hyomandibular canals. 



9. Remains of the cartilaginoiis cranium 



Extensive unossified remains of the chondrocranium are 

 retained in the adult, particularly in the orbital and nasal regions. 

 There is also a thick triangular plate in the cranial roof and a 

 large lateral plate which lines the cranial wall above the auditory 

 recess. In the basal and occipital regions cartilage is limited to 

 the synchondroses of the various articulations. 



The lateral cartilage plate is an important structure in the 

 auditory wall in Pomolobus pseudoharengus but is limited to the 

 neighborhood of the anterior semicircular canal in most other 

 species. Anteriorly, it lines the lateral wing of the frontal bone 

 in its proximal part; further back it overlies the beveled medial 

 surface of the pterotic (fig. 10) and nearly the whole medial surface 

 of the epiotic (fig. 8, LPC). Owing to a deficiency in the 

 lateral part of the epiotic bone, the plate contributes to that 

 part of the exterior surface of the skull which lies at the bottom 

 of the epiotic fossa (fig. 11). It completes the roof of the 

 chamber containing the ampulla of the anterior semicircular 

 canal by bringing across the interval between the falciform 

 process and the opposed edge of the pterotic bone. The anterior 

 semicircular canal passes through this interval and traverses a 



