MtTSTELiTS l;evis. 125 



Gadus with those in Chimsera is evident^ and, if perpetuated, 

 it might easily lead to some confusion. 



It is, moreover, to be remarked that organs 7 and 8 in 

 Gadus, although innervated by terminal branches of the 

 nerve that innervates organs 9 and 10, are separated from 

 those organs by a considerable interval, and that in this, 

 and also in their general position, they seem to belong 

 more to the anterior group of organs than to the posterior 

 one. 



In Batrachus tau Clapp (10) shows a line of surface 

 organs lying along the ventral and posterior margins of the 

 eye, the line being continued backward by two similar sur- 

 face organs that lie in the otic region. This line, or group, 

 of surface organs is unquestionably the homologue of the 

 organs innervated by the so-called inner buccal and otic 

 nerves together of Chimaera, that is, to the postorbital, post- 

 frontal, and otic organs of Amia. The so-called maxillary 

 line of organs in Batrachus would tlien be the homologue of 

 the suborbital organs of Amia, that is, of organs 5 to 10 ; and 

 the antorbital line of surface organs in Batrachus would be 

 the homologue of the antorbital commissure of Amia. It is 

 evident that if the anterior ends of the postorbital and 

 maxillary (suborbital) sensory lines of Batrachus were to be 

 continued forward until they met the supra-orbital line, an 

 arrangement almost exactly resembling that found in 

 Chimsera would arise. 



Regarding the hyomandibular line of selachians it is 

 impossible to judge whether this line is simply the pre- 

 opercular line of Amia, changed slightly in position at its 

 anterior end, or a line formed by some combination of the 

 pre-opercular canal line and the horizontal cheek pit line of 

 Amia. Amia, in which there is such an abrupt and marked 

 difference of level between the anterior end of the pre- 

 opercular canal and the hind end of the mandibular one, 

 might be considered as representing a stage intermediate 

 between the arrangements found in Gadus or Polypteras (6), 

 and the one found in Mustelus, the hyomandibular line in the 



