EASTMAN: CARBONIFEROUS SHARKS. 63 



the median series, it is considered remarkable that the apices themselves, 

 which are sharp-edged and non-blunted, should be comparatively unworn. 

 Biting as they did between the inner faces of the paired series of the 

 opposite jaw, they would have become very obtuse had the creature's 

 fare consisted of hard-shelled prey, such as moUusks or echinoderms. 

 This leads to the inference that Campodus and its congeners were 

 sharks which subsisted chiefly on vegetation which flourished in the 

 Carboniferous lagoons, or else upon soft animal prey. 



The coronal eminences of the median series in Campodus rise verti- 

 cally above the rest of the tooth in the middle line, and are but slightly 

 compressed from side to side. The anterior and posterior edges are 

 prominent, and although faint wrinkles occasionally appear, the edges 

 are not serrated, in which respect they differ from Edestus and more 

 specialized forms. In two other directions is Campodus less specialized 

 than the Edestus-type : the symphysial teeth are, in their entirety, but 

 little laterally compressed ; and, secondly, although their crowns are 

 inclined forward at a steep angle, they do not override one another, and 

 their roots are not produced. 



Antero-lateral series. — We come now to a consideration of perhaps 

 the most important feature displayed by the Kansas example, and that 

 is the natural association of the symphysial with three of the antero- 

 lateral series belonging to either side of the jaw. If, after all that has 

 been said, any doubt remained whether the principal series were truly 

 median and anterior in position, it would be dispelled by a mere inspec- 

 tion of the smaller associated series. It is evident at a glance that the 

 latter are scarcely at all displaced with reference to the median series, 

 except in so far as the cartilaginous rami of the lower jaw have been 

 pressed together prior to fossilization, and hence partly close over the 

 median series behind. The continuity of the calcified cartilage, which 

 supports not only the median but also the antero-lateral series on either 

 side, positively identifies this as the symphysial region. Let the paired 

 antero-lateral series with their supporting cartilage be imagined as 

 opened out horizontally on either hand so as to include about the same 

 angle between them as the jaws of Cestracion, and let these series 

 be continued behind by 18 or more transverse rows of lateral teeth, 

 we shall then have an adequate presentment of the lower dentition of 

 Campodus. 



The antero-lateral series on the right-hand side of the symphysial are 

 more perfectly preserved than those on the left, and are identical in all 

 respects with the teeth occupying a corresponding position in the splendid 



