82 THE ASTEROLEPIS, 



a recipient pit for the accommodation of a tooth in tne oppo- 

 site jaw, immediately behind it. Taken altogether, the alli- 

 gator-like teeth, with the alligator-like pits hollowed for their 

 reception, in the jaws of this ancient fish, bear decided c\i- 

 dence to its reptilian character and standing. 



There was another striking peculiarity of the jaws of Aster- 

 olepis, exemplified in the fine specimen figured here, and in 

 some others in my collection, which extended also to the 

 creature's palate, and which, in a certain degree, we find ex- 

 emplified in the jaws and palates of some of the existing 

 placoids. In most of the placoids, the teeth which are ranged 

 along the jaw or palate, and the shagreen points spread over 

 the skin, seem to be equally of dermal origin, and can be 

 stripped off" with the integuments on which they rest. And 

 so nearly do they approach in character, that there are cases 

 in which they can scarce be distinguished ; — the teeth may 

 be taken for shagreen points, or the shagreen points for teeth. 

 This is strikingly the case in Cestracion Phillippi (the Port 

 Jackson shark). We find immediately within the more cha- 

 racteristic pavement teeth of the animal, osseous points of an 

 irregularly cruciform shape, that might be mistaken for the 

 osseous points, also irregularly cruciform, that form the sha- 

 green which covers its back and sides ; and the palate of 

 Squalina (the angel-fish) bristles as thickly with a shagreen 

 hardly distinguishable from that which the creature wears 

 outside, as any part of its body. Now, encrusting the palate 

 of Dipterus, immediately between the angular patches of 

 teeth, we find exactly the same glossy enamel as that which 

 covers its dermal plates and scales ; the skin within the 

 mouth, if one may so speak, so completely corresponds with 

 the skin outside, that we find it bearing the same rich gloss, 

 and punctulated with the same microscopic tubes. There 

 was, we find, within the mouth of Asterolepis a similar repro- 

 duction of dermal peculiarities. It was lined with osseous 



