322 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



fossiles, vol. Ill, tab. 27, figs. 9 and 11). In the posterior rows 

 of both jaws the cusps of the teeth are not yet developed. 



In the jaws of a 418 mm. (16*4 in.) long young H. PhilUpi, I 

 found in the upper and lower jaw 20 vertical row of teeth. In 

 the upper jaw, the two posterior rows had the character of the 

 large pavement-like teeth, while in the lower, the three posterior 

 rows shewed this character. In the upper jaw, it was the teeth 

 of the last row that were the largest, on the lower, the second 

 last. 



The longitudinal ridge was much more prominent in the 

 posterior teeth of this young animal than in older speci- 

 mens. In the middle row of the upper jaw I have counted six 

 teeth, and five in each of the posterior rows ; in the lower jaw, 

 six teeth in the middle row, and six teeth in each of the posterior 

 rows. 



The anterior teeth of the not fully adult Heterodontus (761 

 mm. long) are distinctly tri-cuspidate (vide fig. 10), while those 

 of the adult become almost pavement-like, with an inconspicuous 

 cusp (fig. 19, A. and B.). 



2. — Dentition op the adult Heterodontus Phillipi. Bl. 



A drawing of the charactestic dentition of Heterodontus is given 

 with the first description of the so-called "Port Jackson Shark."* 

 In different scientific works** there are to be found good figures 

 of the teeth of H. Phillipi, and I would certainly not have been 

 satisfied with so few drawings had I not the intention of 

 writing further on this subject. A few points, not yet decided, 

 prevent me from publishing my results at the present time. 



I will confine myself here to only a few remarks. The number 

 of the teeth, as well as the general form, is, on a cursory glance, 

 almost the same in both jaws, but a closer inspection shows a 

 difierence in both those respects between the upper and lower 

 jaws, and also between different individuals. In one case, I have 

 counted altogether 34 vertical rows in the upper jaw, and 31 in 



* (Vide the Voyage of Governor Phillip to Botany Bay. London, MDCJCLXXXIX, 

 page 283. 



** L. Agassiz. Reuherches sur les Poissons fossiles, tome III, 1833-43, tab D., figs. 

 11-19. R. Owen. Odontography (1840-45) plates 10 and 11 ; and the works of various 

 other authors. 



