DEVONIAN FISHES OF IOWA 251 



the steeply inclined triangular palatine plates that abut against 

 it on either side. The inferior border of the palatines, para- 

 sphenoid and vomer appears to have suffered somewhat from 

 chemical corrosion, in consequence of which no indications of 

 teeth are anywhere visible. Possibly for the same reason no 

 teeth are to be observed along the margin of the lower jaw, nor 

 lying free in the matrix, in case any had been broken off. 



The mandibular ramus of the right side is well displayed, and 

 the dentary is seen to be still in union with its fellow of the left 

 side at the symphysis. The articulo-angular element is long, 

 narrow in front, its superior border rising into a small median 

 and a large posterior elevation, between which is a deep con- 

 cavity ; and its inferior border is nearly rectilinear. The super- 

 ficial ornament of this piece has become well-nigh obliterated 

 by weathering or abrasion, and of the two gular plates immedi- 

 ately underneath, nothing remains but an impression of their 

 inner surfaces. 



A notable peculiarity of the type specimen, one that possibly 

 bears witness to primitive traits, consists in the arrangement of 

 cheek-plates immediately in advance of the operculum. In all 

 other Coelacanths so far as known, two postorbital plates of 

 subequal size are placed one above the other in the space be- 

 tween the orbit and operculum, in such fashion that the small 

 triangular plate called "postmaxillary" by Huxley is excluded 

 from contact with the operculum. The new Kinderhook species, 

 however, has all three of these cheek-plates situated in vertical 

 series, one overlapping the other from above downward, and 

 each overlapping the anterior border of the operculum. The 

 lowermost cheek-plate, that corresponding to the so-called "post- 

 maxillary" of Huxley, terminates below in line with the inferior 

 border of the operculum, and covers the space immediately be- 

 hind the inflected portion of the articulo-angular element of the 

 lower jaw. Its antero-superior margin is apposed to the 

 strongly arched, probably semicircular suborbital element, of 

 which only a small segment is preserved in the type example. 

 In this latter respect the plate in question is seen to occupy the 

 same relation as the "postmaxillary" of other Coelacanths. 

 Owing to the fact, however, that in later species this plate is 



