green: ENCHODUS in KANSAS MUSEUM. 77 



Doctor Hay (1903) says there is probably an alternation in 

 the replacement of the palatine fangs. None of the specimens 

 in this collection show this in any marked degree. The fangs 

 do not vary even in the larger species, as Enchodus dints and 

 Enchodus petrosus, more than one or two millimeters. This 

 slight inequality comes easily within the limits of individual 

 variation. In no case is there a process of bone extending for- 

 ward over one fang and not over the other, though several shov/ 

 such processes projecting over both fangs. However, these 

 seem to the author not to be the beginnings of the new fang. A 

 study of longitudinal median sections and coronal sections of 

 the palatine would indicate that they have a different origin. 

 These overhanging processes, which are composed of true bone, 

 are so far above the osteodentine of the palatine that it seems 

 improbable that they have anything to do with the develop- 

 ment of the fangs. The palatines which have this process are 

 quite different internally from those which do not possess it 

 Figure 15, plate VH, is nearly a median vertical section of a 

 palatine not having the process, and figure 17 of the same 

 plate is a similar section of a palatine which has it. Certainly 

 this bony process does not grow down and form a tooth of 

 osteodentine. From the shape of the areas, a, b, c, d, etc., in 

 figure 17, it would appear that the cephalo-dorsal process over 

 a, the base which functioned last, was present over each of the 

 other bases, b, c, d, etc., when they were functioning bases, 

 i. e., it was continually present, and that it never was present in 

 the palatine shown in figure 15. Several palatines were sec- 

 tioned thus by the writer ; although not enough evidence can 

 be adduced from the material in hand to make the conclusion 

 positive, the study would indicate that the cephalo-dorsal proc- 

 ess and the type of internal structure found in the palatine, 

 shown in figure 17, are constant correlatives. Moreover, it 

 seems to the author that the new bases are not formed by a 

 fold growing down from above, but that there appears over 

 the mesial, cephalic, and to some extent external, portion of the 

 mass of osteodentine a gradually thickening layer of osteoden- 

 tine, deposited by the odonto-blastic tissue which must have 

 covered these surfaces, the most cephalic portion developing 

 fastest, until the new base was of sufficient size to support the 

 new fang. 



2-Univ. Sci. Bull.. Vol. VH, No. 2. 



