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TEXTBOOK OF ZOOLOGY 



side is the anterior fontanelle. The nasal capsules are rounded, car- 

 tilage-encased cavities, one at each side of the base of the rostrum. 

 These capsules house the olfactory sense organ in life. The orbits 

 are laterally located, spherical depressions which normally hold the 

 eyes. Each orbit is guarded anteriorly, dorsally, and posteriorly by 

 slight extensions of the cartilage known as preorhital process, supra- 

 orbital crest, and postorbital process respectively. The orbits are 

 laterally located spherical depressions in which the eyes are set. 



aosTuuM 



OLFACTORY 

 CAPSULE 



EPIPHYSIAL 

 FORAMEN 



LATERAL 

 LINE FOR^M^^»A 



ENDOLYMPHATIC 

 DUCT 

 ORblT 



OPT\C 



FORAMEN 



PTERYOO- 

 QU ADR ATE 

 MECKELIAN 

 CARTIlAOE 



CERATOHYOID 

 HYOMANDl&ULAR 



CERATO- , 



&RANCH lALS 



EPI- 

 BBAMCHIALS 



CAROTID 

 FORAMEN 



PHARYNGO-J 

 BRANCH I ALS \. 

 OTIC 

 CAPSULE 



Fig. 230. — The skull and visceral arches of the dogfish shark, Sqimlus acant.hias. 

 Dorsal view above, ventral view below. Latei'al aspect on the riglit. (From 

 Atwood : Introduction to Vertebrate Zoology, published by The C. V. Mosby 

 Company. ) 



The visceral skeleton consists of the upper jaw (palatopterygoid 

 or quadratopterygoid cartilages), lower jaw (Meckel's cartilages), 

 hyoid arch (hyomandibular, ceratohyal, basihyal), and five branchial 

 arches (each typical one has pharyngobranchial, epibranchial, cera- 

 tobranchial, hypobranchial, and basibranchial cartilages). 



