76 KANSAS UNIVERSITY SCIENCE BULLETIN. 



scar is frequently to be observed a small opening. These open- 

 ings show much more plainly in some specimens than in 

 others. In many they are closed, and their former positions 

 are indicated by a dark spot on the surface (pi. XV, fig. 15). 

 The line A-0, in plate VII, figure 1, very nearly coincides with 

 a horizontal plane passing through these openings, the ce- 

 phalic three of which are indicated by the letters b, c, and d. 

 A detailed description of the internal gross structure and de- 

 velopment of this interesting element is given in the explana- 

 tion to plate VII. 



The replacement of the palatine fangs has been described 

 substantially in the following words by Doctor Loomis : 



On the anterior end of the palatine there is developed a fold of os- 

 seous tissue, which grows downward until it overhangs the palatine 

 fang. This fold is somewhat larger than the base of the senescent fang, 

 and a wing of it extends posteriorly on both sides of the old base. Thus 

 as the new base develops the palatine increases in size. From the ven- 

 tral margin of this fold the new fang develops. 



It has not been determined at just what stage the senescent 

 fang is lost. One of the specimens has the basal portion of 

 the old fang still present, the old fang having been broken off 

 about two millimeters from the palatine (pi. XV, fig. 14). In 

 this specimen it seems that the senescent fang must have per- 

 sisted until quite a late stage in the development of the new 

 tooth and then to have been broken out. This, as well as the 

 similar cases where two teeth are found standing closely ap- 

 posed on the ptergoid, would indicate that the swollen bases of 

 the old teeth are not absorbed until after the new tooth is 

 developed. One might expect to find in a large collection of 

 specimens a few that would show the enlarged base of a tooth 

 in the process of absorption. Such specimens are at hand. 

 The conditions of the bases of the discarded teeth vary from 

 a state in which a part of the basal portion of the tooth is still 

 present to almost complete absorption. The absorption process 

 continued throughout a longer period of time than was con- 

 sumed in the development of three new fangs. This fact is in- 

 dicated by the portions of old bases which are to be found just 

 caudad to the fang, the ventral surface of the palatine becom- 

 mg smooth only posterior to the third or fourth scar. The bases 

 of palatine and dentary fangs are never completely absorbed. 

 (See pi. VII, fig. 15, and pi. II, fig. 2.) A dentary, described 

 below, shows very strikingly this slow process of absorption. 



