THE CLUPEOID CRANIUM AND THE SWIMBLADDER 463 



canal in the cartilage plate until it reaches the edge of the epiotic 

 where it passes under a hook-like process from that bone and 

 emerges to the cranial cavity. The cartilage plate also con- 

 tributes a small part to the roof of the lateral recess. 



10. The lateral recess 



This is an almost isolated cavity between the sphenotic, 

 pterotic, and prootic bones and lateral wing of the frontal. It 

 communicates medially with the utricular portion of the auditory 

 recess through the low arch under the falciform process. The 

 only other openings to this recess are through the foramina for 

 the lateral-line canals in the lateral wing of the frontal bone, i.e., 

 through the foramina for the exit of the suborbital and hyoman- 

 dibular lateral-line canals and through the channel for the supra- 

 orbital canal as it arches up over the eye. By means of these 

 canals it communicates immediately with the exterior. The 

 recess contains a large sac-like expansion of the lateral-line canal 

 from which the above-mentioned canals are given off. The 

 rest of the recess is filled with a reticular-like connective tissue 

 which is continuous through the arch with the perimeningeal 

 tissue in the auditory recess. In this tissue is a large perilaby- 

 rinthine space limited by a well-defined marginal membrane 

 (fig. 9, PS). The tissue is traversed by a recurrent lateral-line 

 branch of the facial nerve which gains access to the recess through 

 articulation between the prootic and sphenotic bones (fig. 3). 



11. The temporal foramen 



This is a characteristic feature of the clupeoid skull. It is a 

 very large foramen in the upper part of the temporal fossa of the 

 skull between the frontal, parietal, epiotic, and pterotic bones 

 (fig. 1, TF). It is filled with adipose tissue which is continuous 

 with, and apparently a part of, the perimeningeal tissue within 

 the cranium. Previous writers have overlooked the fact that 

 imbedded in this tissue, and nearly coterminous with the margin 

 of the foramen, is a large bay-like expansion of a lateral-line 

 canal. 



