in the Mandilular Arch of Cliiinaiva moiiHtrosa. Ill 



shows tlie body of the narrow tail-like portion and the 

 termination of tlie dorsal plate (fig. 3 I). 



Fi-. 2. 



af>.6. 



Abnormal bone, first ca^ e. 



a, triangular anterior portion ; b, tail-like posterior portion ; 

 d.pl., dorsal plate ; liy., ligament. 



Fi-. 4. 



Fiii-. 3. 



1 



ab.b. 



Fig. 3. — Sections, («)tbrougli the triangular anterior portion, {b) turoiigli 

 the tail-like posterior portion. Marked a and b respectively 

 in tig. 2. 



Fig. 4. — Abnormal bone, second case, ab.b., abnormal bone; lig., liga- 

 ment. 



In the .second specimen the hone consists of a thin plate- 

 like stiuctiue, having the appearauce, when looked at from 



