694 



Bashford Dean Memorial Volume 



Test-ngure 26. 



Dentition of Heterodontus japonicus: A, upper 



jaw; B, lower jaw. Dra^sTi from the young female 



spedmen, 406 mm. (16 indies) long, shown in 



Text-figures 23 to 25. 



After Maday and Madeay, 1SS4, 



Figs. 4a aad 43, pL 20. 



an impression that it is inaccurate in several 

 respects. The eye is too large and too near 

 the top of the head: the supraorbital ridge is 

 omitted or represented as part of a circular 

 ridge extending entirely around the eye. The 

 notch in the ventral lobe of the caudal fin is 

 curved instead of angular. The dark brown 

 transverse stripes are more regular and less 

 numerous than in any other drav-nng of this 

 species. For these reasons this figure is not 

 reproduced here. The legend states that the 

 species is not good for food — contrar^T- to the 

 statement in Siebold's "Fauna Japonica"'. "De 

 gustihus non est disputandum" . 



Teeth. — In Maclay and \Iacleay"s young 

 (16'inch) female specimen of the Japanese Bull- 

 head Shark, there are 23 transverse rows of 

 teeth in both upper and lower jaws (my Text- 

 figure 26). The anterior (cuspidate) teeth are 

 r\^pically five-cusped. In the upper jaw, the 

 number of teeth in the central row is eight (one 

 is not visible in Text-figure 26). In the lower 

 jaw, the transition betw^een anterior (cuspidate) 

 and posterior (grinding) teeth is very abrupt; 

 in the upper jaw^ it is more gradual. In making 

 comparisons unth the teeth of other Hetero- 

 dontid sharks, it should be borne in mind that 

 \Iaclay and Macleay's description is based on 

 a single specimen, and that this specimen was a 

 decidedly young one. 



The development of the teeth of Hetero- 

 dontus japonicus is further described in the final 

 section of this article, ■w.-hich contains also a 

 concise summary of the main course of develop- 

 ment of the teeth of the entire genus. 



.'YFFINITIES TO FOSSIL FORMS 



In the introduction to this article I have 

 pointed out that the genus Heterodontus in- 

 cludes some fossil forms, so that the paradoxi- 

 cal term "living fossils" might pardonably be 



