The Latero-Sensory Canals and Related Bones in Fishes. 413 



of the point of tlie first mandibular tooth, lies immediately antero- 

 mesial to this part of the canal, the canal running postero-mesially 

 between the two perforations. The canal then traverses the entire 

 chain of so-called maxillary bones, and then the preorbilal, sub- 

 orbital and postorbital bones of Parker's descriptions, as fully shown 

 in the accompanying figures. The number and position of the sense 

 organs in this part of the canal of the adult, and also that of the 

 organs in the other canals, could not be determined from the skeleton. 

 The several bones that form the chain of so-called maxillary 

 bones of Lepidosteus evidently contain latero-sensory components that, 

 in other fishes, go to form a part of the chain of infraorbital bones, 

 and they occupy a place in that chain that is ordinarily occupied by 

 the lachrymal bone alone. But these latero-sensorj^ components have, 

 in the adult Lepidosteus, fused completely with certain tooth-bearing 

 plates, for each bone of the series bears a double row of teeth; a 

 marginal row of small teeth, and what Parker calls a *' submarginal 

 row" of large ones. Of these latter teeth Parker says [58, p. 446] 

 that the "superficial palatine", on each side, helps to cany them; and 

 in his figures of transverse sections of young Lepidostei (fig. 3, pi. 33, 

 and fig. 2, pi. 35) he shows the teeth borne b}- plates that are 

 superficially related to the palato-pterygoid cartilage, and entirelj^ 

 separate from the so-called maxillaries. This led me to suggest, in 

 an earlier work [7], that these submarginal teeth might be dermo- 

 palatine teeth, and as such I am still inclined to consider them. But an 

 examination of my specimen shows that, in the adult, the plates that 

 bear the teeth are wholly fused with the latero-sensory ossicles, 

 and wholly free and independent of the closely applied, and 

 immediately internal, so-called superficial palatine. Moreover, this 

 latter bone of the adult, and also that of Parker's oldest larva, must 

 represent the deeper part only of the so-called superficial palatine of 

 his sections of a 2'/„ inch larva, as comparison of the several figures 

 will show; and this deeper bone may accordingly be an ecto-pterygoid, and 

 not a palatine at all, the palatine elements then having fused with the 

 latero-sensory ossicles to form the so-called maxillaries. Those bones 

 of my two adult specimens that correspond to the palatines of Parker's 



