The Structure of Dinichthys 



149 



Text-figure 30. 

 The infero'gnathal and postero-infero-gnathal elements of Dinichthys mterrnedius Nwb., outside view. 



A, functional portion; B, blade; C, PIG; a, front "tooth"; b and c, tooth-like indentations on cutting part; b-c-e, cutting part; d, 



tubercles; im, joint impression on PIG. 



Text-figure 31. 

 The infero-gnathal and postero-infero-gnathal plates of Dinichthys intermedius Nwb., inside view. 



A, functional portion; B, blade; C, PIG; a, front "tooth"; b and c, tooth-like indentations on cutting part; b-c-e, cutting part; d, 

 tubercles; fl, "floor" between blade and cutting part; tl{, thickening consoUdating the second indentation. 



composed of a long, thin blade (Text-figures 30 and 31 B) and of a solid, thick functional 

 portion (Text-figures 30 and 31 A). These two parts are very sharply divided from the 

 outside. It looks as if the functional portion is a separate plate placed on the blade. But, 

 as Hussakof noted in 1906, these two portions in reality form one bone with one ossifica- 

 tion centre. This is, however, very clearly seen on the inside. 



Of course, unlike ASG and PSG, the functional portion of IG has the worn area on 

 the outside and is smooth on the inside. It is composed of a big front ''tooth" (Text- 

 figures 30 and 31 a) and a cutting part (Text'figures 30 and 31 b, c, e). The front "tooth," 



