274 



bones of Amia and Teleosts, for, aside from the facts that they have 

 inamoveable relations to the skull, and are traversed by a lateral canal, 

 other and apparently true maxillary bones are found in what would 

 seem to be their proper places. Immediately mesial to the row of 

 small teeth found on the ventral edge of this maxillary chain of bones 

 there is a row of larger teeth, but whether these latter teeth belong 

 to the bones of the maxillary chain, or to the adjoining auto- or dermo- 

 palatines, I am wholly unable to judge. They are apparently dermo- 

 palatine teeth, for van Wijhe says (No. 47, p. 266) that the auto- 

 palatine teeth are small. If they be such teeth, and if the derrao- 

 palatines of the fish were to fuse with the so-called maxillary chain 

 of tooth-bearing canal bones, a bone would arise that would corre- 

 spond strikingly to a part of the so-called maxillary bone of Polypterus, 

 excepting only in its possessing two rows of teeth instead of one. 



We thus seem to have, in Lepidosteus, a fish in which a com- 

 bination of canal bones and dermopalatine tooth - bearing plates have 

 pushed the piscine maxillary bones out of what is assumed to be their 

 primary relations to the gape of the mouth; and if the maxillary bones 

 should disappear, or become absorbed in the bones of the cheek, as, 

 for example, in such a bone as bone Y" of Polypterus, the tooth- 

 bearing part of the upper jaw of Polypterus would arise. And in this 

 connection it is to be noted that the tooth-bearing part of the maxil- 

 lary of Polypterus ends abruptly at the level of the hind end of the 

 suborbital canal component of the bone, as is definitely indicated by 

 the position of tube No. 7 infraorbital. 



In Acipenser the maxillary fold must certainly be represented in 

 that dermal fold that is shown by Parker (No. 30) extending across 

 the snout of larvae, in front of the barbels of the fish, and then back- 

 ward below the eyes. The median part of this fold would then prob- 

 ably be the anlage of the premaxillary bones, which are actually 

 wanting in the fish, and the vomers, lying posterior to the barbels, 

 between them and the anterior edge of the suctorial mouth, would 

 have to the premaxillary anlage their proper relations. The so-called 

 maxillary bones of the fish would then be palatine, or pterygo-palatine 

 ones, as the evident relationship of the fish to Selachians would nat- 

 urally indicate that they should be. 



All these various considerations seem to me to strongly indicate 

 that the tooth - bearing part of the so-called maxillary bone of Poly- 

 pterus is not a Teleostean maxillary one. Such being the case, a com- 

 parison with Lepidosteus clearly indicates that it must be a dermo- 

 palatine, which bone is otherwise wanting in Polypterus. The palatal 



