222 JouRNAL OF CoMPARATIVE NEUROLOGY. 
cates with the surface by a short tubule, passing directly outward 
through the dermis. 
There is an irregular line of large pit organs near the dorsal 
median line of the trunk, the first four organs of which are in- 
dicated at d. 7. on Fig. 1. These are all innervated from the r. 
lateralis vagi and evidently correspond to the dorsal pit line of 
Amia (ALLIs, ’89) and Batrachus (Capp, ’99) and to the row 
of pit organs in the corresponding position in Gadus. The 
scattered naked neuromasts described above in connection with 
the r. lateralis vagi which accompany the course of the lateral 
line of the trunk appear to correspond to the accessory lateral 
lines which have been found by numerous observers accompany- 
ing the lateral line of various fishes, for example Fierasfer 
(Emery, ’80). Among the siluroids EIGENMANN (’g0, p. 315) 
describes an extreme form of this in the South American form 
Hypopthalmus, where accessory lateral lines intersect the main 
lateral line so as to form a lattice-work. 
In Ameiurus melas the canal systems of the two sides of 
the body do not communicate by means of commissures at any 
point. The row of large pit organs across the premaxillary 
corresponds in positionto the premaxillary and ethmoid com- 
missure of Polypterus (ALLIS, ’00) and of some other fishes. 
The short segment of the supra-orbital canal leading to pore V 
and the related anterior pit line (a. 7, Fig. 1) may represent a 
vestige of a similar commissure. There is no occipital or supra- 
temporal canal, nor is there any vestige of such a canal, unless 
the occasional presence of the minute extra-scapular bone dis- 
cussed above is to be regarded as such. And in none of the 
forms which I have examined is there a pit line which can be 
identified with the: posterior pit line of ALLis, which in several 
recorded instances accompanies the occipital commissure. But 
there is in nearly all specimens of North American siluroids - 
which I have examined either microscopically or macroscopical- 
ly a well marked pit line consisting usually of two large pit 
organs on each side forming a transverse line across the top of 
the head a very short distance caudad of the union of the oper- 
cular canal with the main canal in the squamosal (or the first 
