THE CLUPEOID CRANIUM AND THE SWIMBLADDER 



457 



small, ventrally directed foramen; from it also the ramus sympa- 

 theticus and the ramus pretrematicus for the pseudobranch pass 

 in a bony canal over the anterior medial surface of the bony 

 capsule to the ventral surface of the skull (fig. c). 



Lateral to the ganglionic fossa a rather thick process of bone 

 articulates with the sphenotic. The orbital surface of this proc- 

 ess has a large groove for the maxillomandibular nerve. The 

 base of the process is penetrated by a canal which passes laterally 



Fig. c Ventral surface of the middle region of the skull, showing the relations 

 of the trigeminofacial ganglia and their branches to the prootic bone. Based on 

 figure 7. Diagrammatic. Abbreviations on page 473. 



over the anterolateral surface of the osseous capsule from the 

 ganglionic fossa to the ventral surface of the skull. Through 

 this canal the hyomandibular ramus of the facial nerve is' con- 

 ducted to the inside of the gill cover. 



The relations of the ganghonic fossa recall the 'trigemino- 

 facial chamber' of Allis ('03) and suggest the possibility of the 

 homologj: of the capsule with a portion of that chamber. Knowl- 

 edge of the development of the clupeoid skull is necessary, how- 

 ever, before this suggestion can profitably be considered. 



On the ventral surface of the prootic bone, the medial plate is 

 separated from the remainder of the bone by the broad, thin 



