Nos. IAXD2.] ANATOMY OF SCOMBER SCOMBER. 185 



like mass that covers externally this part of the canal, just as 

 similar systems have been obliterated in the postorbital part of the 

 main infraorbital canal. 



In ChUnccra, according to Cole (No. 15), the preoperculo- 

 mandibular canal is represented by two separate canals, called by 

 him the hyomandibular canals. Each of these canals arises, 

 independently, from the superior division of the infraorbital canal 

 of the fish, one immediately anterior to the first otic organ and 

 the other immediately posterior to that organ. From the anterior 

 one of these two canals, at about the middle of its length, a so-called 

 inferior division of the buccal part of the main infraorbital canal 

 has its origin. This inferior buccal canal is said by Cole to have 

 been found by Carman, in a specimen examined by that author, 

 arising from the main, or dorsal buccal canal, instead of from the 

 anterior hyomandibular one. The inferior buccal canal is said by 

 Cole to be innervated by two separate branches of the outer 

 buccal nerve; which indicates clearly that it has developed from 

 two separate centers. This inferior buccal canal and the anterior 

 hyomandibular one would therefore seem to together represent 

 some combination of the cheek lines or pit organs of Amia and 

 one or more of the anterior groups of infraorbital organs of Auiia 

 and Scomber. As the anterior hyomandibular line seems also to 

 have arisen from two centers, and as there are two separate groups 

 of ampullary organs associated with it, this line may represent the 

 cheek and mandibular organs of Amia, the posterior hyomandib- 

 ular line then alone representing the preopercular line of Amia. 

 It is to be remembered, in this connection, that the vertical pit line 

 of the cheek of Amia ends dorsally among the pores of group 12 

 infraorbital (No. 2, p. 506). 



In Necturus the hyomandibular sensory line of Piatt's descrip- 

 tions is apparently the homologue of the entire preoperculo-man- 

 dibular canal of Amia, and the mandibular line the homologue of 

 the cheek and mandibular lines of pit organs. The development 

 and innervation all tend to show this, and I have already referred 

 to it in an earlier work (No. 7). The anterior, or mandibular 

 part of the hyomandibular line of Necturus is said by Piatt to arise 

 independently of the posterior or hyoid portion, developing in 

 connection with the anterior end of the ventral longitudinal ridge 



