SENSE ORGANS OF AM1URUS. 265 



tion of hyoruandibular. With Bodenstein I find no communication 

 between the principal canal and that which is lodged in the preoper- 

 culum and mandible opening with eight pores on either side. (Figs. 

 5 and 6). 



From the hyomandibular articulation the canal passes forwards 

 and inwards giving off the infraorbital branch which passes through 

 the infraorbital chain of bones and terminates in the adnasal or 

 antorbital bone, which is the most anterior of these. In its course 

 the infraorbital canal first opens directly behind the eye, then by 

 two pores below it and one in front, and finally by two in the same 

 transverse plane behind but lateral to the anterior nasal aperture. 

 The supraorbital canal may be regarded as the continuation of the 

 principal canal ; immediately after giving off the infraorbital branch, 

 a tube is directed backwards which opens behind the first infraor- 

 bital pore, but near the middle line. From this point the canal 

 inclines distinctly towards the middle line, opens by a pore in the 

 plane of the eyes, by another medial to the posterior nares, and 

 terminates by two pores which lie in the same sagittal plane over 

 the medial division of the nasal sac. No further communication 

 takes place between the supraorbital and infraorbital canals of the 

 same side, nor do the supraorbital canals of opposite sides meet in 

 the middle line as in Cottus. The chief departure from Wieder- 

 sheim's diagram (p. 359 I. c.) consists in the independence of the 

 mandibular branch, and the absence of an anterior anastomosis of 

 the infra- and supraorbital branches — features which are common to 

 Amiurus and Cottus. On the other hand, Cottus differs from 

 Amiurus in possessing one median and two lateral pores in the occi- 

 pital commissure, and in the supraorbital branches meeting each 

 other in the middle line before they give off a single backwardly- 

 directed tube in place of the two noted above. 



(2). Accessory Lateral Organs. 

 In various Teleosts the lateral line is not an uninterrupted canal 

 as in Amiurus, but may be regularly interrupted as in Esox, two or 

 more uncanaliculated scales separating those which are canaliculated. 

 " As if in compensation, however," says Leydig 1 , " additional scat- 

 tered canaliculated scales are present above and below the lateral 

 line, to a certain extent accessory or rudimentary lateral lines, as 



1 1. e. p. S3. 



