DEVELOPMENT OF TEETH IN HATTEEIA PUNCTATA. 185 



observations on the subject of such ingrowths. Here on 

 the vomers there are several of these structures at various 

 points. Anterior to each tooth is a thin, flat band of epi- 

 thelial cells lying freely below the epidermis, and continuous 

 posteriorly with the epidermal cells in contact with the teeth. 

 I am inclined to regard this as dental in its nature, and as 

 pei'haps giving rise to the occasional anterior small vomerine 

 tooth described (on one side only) by Baur (7) and Siebenrock 

 (4). There are no indications of this tooth in my specimen. 



The larger specimen of the last two examined measured 

 21*2 cm. in total length, and 9 cm. from tip of snout to ante- 

 rior border of pelvic girdle. 



In this individual, as in the last, each premaxilla has two 

 teeth projecting beyond the gum. A microscopic preparation 

 of the right side, however, shows that they are not the same 

 in the two specimens (fig. 22). The following is my inter- 

 pretation of the tooth change here, although it is possible 

 that other successional teeth may have intervened between 

 the conditions shown in figs. 21 and 22. I believe that No. 3 

 of the newly-hatched animal has now been shed, and is re- 

 placed by the second successional tooth {t. s. 2). The first 

 successional is still in place, but it is on the point of beino- 

 shed to make way for the third (/. .'^. 3), which is nearing the 

 surface. I have confirmed the appearances seen in this 

 entire preparation by sections through the left premaxilla. 



In the maxilla there are thirteen and fourteen teeth 

 respectively on the two sides (fig. 27, for the left side). 

 Throughout the whole length a large alternates with a small 

 tooth. An entire preparation of the left side shows that the 

 anterior portion is undergoing tooth change. In addition 

 to the first successional {t. s. 1) seen in the last specimen, the 

 second in order is now also a successional tooth [t. s. 2). 

 Judging from its size and extent it has replaced two teeth 

 of the earlier set. Finally, there is a third successional tooth 

 (t.s.'o) lying deeply seated above the fourth in order, and 

 pointing with its apex towards the fifth. I have not found 

 any indication of a tooth change posterior to this point up to 



