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Bashford Dean Memorial Volume 



figure (my Text-figure 33). According to Huxley, the hyomandibular is of moderate 

 sizie; it articulates with a process on the underside of the auditory capsule and supports 

 the posterior end of the palatoquadrate, with which it is connected by a strong ligament- 

 ous capsule. The huge palatoquadrate is connected with the cranium in the preorbital 

 region by a broad joint (ethmoidal articulation) and in the orbital region by fibrous tissue. 

 The postorbital region of the cranium of Heterodontus appears short, and the preorbital 

 region long, as compared with most sharks. The cranium as a whole is much longer than 

 the jaws, which appear as if thrust forward. Anteriorly the upper jaw extends almost or 

 quite as far as the snout, but posteriorly it does not reach the auditory capsule. Thus the 

 lower end of the hyomandibular cartilage is pulled forward. 



In sharks of the genus Hyhodus, according to Woodward (1916), the pterygoquadrate 

 (palatoquadrate) is not articulated with the preorbital region of the cranium (as it is in 

 Heterodontus). In Hyhodus haujfianus, according to Jaekel (1906), the suspension of the 

 jaws is amphistylic (my Text-figure 28, page 695). The skull of Hyhodus duhrisiensis, as 

 described by Woodward (1886) is even more typically amphistylic, resembling that of 

 Heptanchus. Woodward's figure shows the palatoquadrate with a small but definite 

 facet in position for a postorbital articulation with the cranium; the hyomandibular is 

 slender, but evidently gives some support to the jaws. But in Hyhodus hasanus, as 

 described by Woodvv^rd (1916), there is no articulation between the palatoquadrate 



mfc 



Text-figure 32. Text-figure 33. 



Incomplete skulls of Scyllium and Heterodontus, illustrating methods of suspension of the jaws. 

 Text-figure 32. The skuU of Scyllium, illustrating the hyostyHc method of suspension of the jaws. 



a., auditory capsule; ch., ceratohyal cartilage; or., cranium; ep., ethmoid process; h., hyomandibular branch of facial nerve; hm., hyoman- 

 dibular cartilage; 1., labial cartilage; m\., Meckel's cartilage; rm., nasal capsule; q., quadrate region of the palatoquadrate cartilage; 



r., rostral process; sp., spiracle. 



After Goodrich, 1909, Fig. 59c. 



Text-figure 33. Cranium, jaws and hyoid arch of the Port Jackson shark, Heteroaontus phillipi. 



a., auditory capsule; ch., ceratohyoid; ea., ethmoid articulation; hm., hyomandibular; 1., labial cartilage; m\., Meckel's cartilage; 

 na.. nasal capsule; nc., nasal cartilage; q., quadrate region of the palatoquadrate; pc., prespiracular cartilage. A dotted ring behind 

 the prespiracular cartilage indicates the position of the spiracle. 

 After Goodrich, 1909, Fig. 5S.-i. 



