DEVELOPMENT OF TEETH IN HATTERIA PUNCTATA. 167 



paper refers to " Epitlielwucherungen/' whicli are formed 

 before the ingrowth of the dental lamina and which pro- 

 ject above the surface of the mucous membrane ; it is not 

 easy to be sure when he is speaking of these, and wheu of 

 the papilla3 produced by the presence of an enamel organ of 

 the first series.^ In a recent paper, Laaser (15), in de- 

 scribing the development of the dental lamina in Spinax 

 niger, says : " Die ersten Zahne liegen also meist am 

 Uebergang vom ausseren Zahnepithel zur Zahnleiste ; " and 

 his fig. 4, showing the enamel organ of such a tooth, is 

 almost a fac-simile of my fig. 1. Here, then, Ave have a 

 Selachian whose first teeth originate in the same way as do 

 those of Hatteria, and in neither case can we accurately 

 speak of development " durch Verkalkung von frei liber die 

 Schleimhautoberflachehervorragenden Schleimhautpapillen." 



In addition to the marginal teeth of the upper and lower 

 jaws, there are present in a position slightly posterior and 

 external to the choana3, two calcified teeth of the first series, 

 one on each side. As is seen from an examination of later 

 stages, this situation corresponds to the anterior extremity 

 of the line along which the palatine dental lamina is subse- 

 quently formed. It is interesting that each of these teeth is 

 situated within a prominent papilhi, but owing to the lack of 

 sections showing their development 1 am unable to say what 

 is the time of origin of the papilla, i. e. whether before or 

 after the tooth is formed. 



Taking all points into consideration, the teeth of this 

 series seem to resemble more closely those of Iguana tuber- 

 culata than those of the Crocodile. The latter in particular, 

 according to Ruse, form a '^Cemeutsockel," and are eventually 

 removed by absorption within the mesoderm. In Hatteria, 

 on the contrary, no such substance is produced, and instead 

 of passing deeper into the mesoderm the teeth are moved 



' In Hatteria the apex of most of these papillae is certainly in the form of 

 a small group of cells (not siiown in my fig. 1), which suggest "Epithel- 

 wucherungen." These may correspond to what Hose describes, but my 

 specimens do not enable me to say whether they arise before the enamel 

 organs are formed. 



