28 CATALOG OF FOSSIL FISHES IN THE MUSEUM 



lines of wear. The form of the element is well shown in 

 Plate 5, figure 3. It will be seen that it is rather broad, 

 and. that its parts are less differentiated than in £)mfc/f- 

 thys\ hence that it is more primitive than the element in 

 the latter genus. The process for attachment is, how- 

 ever, well developed. 



Measurements mm. 



Height (including process and allowing 1 mm. for the 



missing tip) 25 



Greatest width 18 



Height of worn area 9 



Width of process 7 



Left Postero-superognathal (PSG). — This, like the pre- 

 ceding element, is shown in inner view (PL 5, fig. 2). It 

 resembles the same element in Dinichthys. The func- 

 tional margin shows prettily the lines of wear produced 

 in grinding against the mandibular cutting edge. These 

 lines, it mav be mentioned, are,, both in this element and 

 in the antero-superognathal, all vertical and parallel to 

 one another, thus proving that the movement of the 

 upper "teeth" against the lower was vertical, with little 

 or no lateral motion. It is noteworthy that the cutting 

 margin is not uniform in width throughout, but that the 

 anterior half is nearly twice as high as the hinder half, 

 there being an abrupt change from the one to the other. 

 (PI. 5, fig. 2). But whether this feature was pathologic 

 in this specimen, or a constant feature of the species can- 

 not be said. At the posterior end of the cutting margin 

 are two weU-developed denticles. 



Measurements mm. 



Length, antero-posteriorly 27 



Total height (end of process lacking) 22 



Maximum height, exclusive of process 19 



Height of wearing margin in anterior half of." tooth "... 5 



Height of wearing margin in posterior half of ' 'tooth " . . 3 



Left Antero-ventrolateral (AVL). — This plate is incom- 

 plete, only the anterior two-thirds being preserved; it is 

 shown in outer view. As far as preserved it agrees in 

 form with that of the almost complete Coccosteus in the 



