The anatomy op A hammerhead shark. 



973 



Cartilage, the auditory process {ct. p. \ which arises from theantero- 

 dorsal corner of the auditory capsule. The auditory process 

 broadens out distally, and the broad distal portion forms the 

 posterior fourth of the orbit. The process throughout its length 

 acts as a support to the posterior border of the hammer. The 

 relations of this bar and the shape of the orbit are incorrectly 

 figiu-ed by Gegenbaur (5). 



The olfactory capsules are dorso-ventrally flattened and project 

 laterally from the front of the cranium. They do not come 

 into apposition with one another in the median longitudinal line. 

 Each cartilaginous capsule is completely closed except for the 

 small nostril, which is situated a ntero- ventral ly and a short 

 distance from the distal end. 



Text-figure 2. 



Dorsal View of Skull. 



a.f. anterior foiitanelle. 

 a:p. auditor}' process. 

 d.r. dorsal bars of rostrum. 

 n.f. nerve foramen. 

 o. orbit. 



o.c. olfactory capsule. 

 p.a.d. pre-auditory depression. 

 p.f. posterior fontanelle. 

 p.o. post-olfactory process. 

 v.r. ventral bar of rostrum. 



The cranium is slightly dome-shaped dorsally, and the auditory 

 capsviles are attached to it postero-laterally. Between the two 

 auditory capsules, and on the dorsal surface of the cranium is a 

 shallow median depression, the jyosterior fontanelle (pf). This 

 fontanelle contains four apertures, two on each side, which will 

 be referred to later in the description of the membranous 

 labyrinth. 



Each auditory capsule exhibits on its dorsal surface a supra- 

 auditory process {sa.p.) which extends upwards from the socket, 

 which is found on the side of the capsule, for the articulation of 

 the hyomandibular. About half an inch mesial to each supra- 

 auditory process is a small foramen for the passage of a nerve. 



