No. 3.] PHOSPHORESCENT ORGANS. 675 



The temporal canal (PI. XXXVIII, Fig. 3, t) corresponds to 

 the squamosal of AUis in Amia. It contains a single canal organ. 

 Above this canal are two free organs. The infraorbital, temporal, 

 scapular, and dorsal form a continuous series of sense organs. 



A short maxillary canal, mx, with two organs, extends along 

 the maxillary bone below the posterior nasal opening. At its 

 lower end are two free organs with a small phosphorescent 

 organ above each in very old specimens. 



A malar row of sense organs, ma, extends downward from the 

 suborbital across the cheek to the angle of the mouth, thence 

 along the mandible over the operculo-mandibular canal to its 

 anterior end. There are thirty-one organs in this row, thirteen 

 in the malar portion and eighteen in the mandibular. Two 

 spurs are connected with this line, a short anterior spur of two 

 organs from the middle of the cheek portion of the line and 

 a second posterior one of four to five organs from the angle 

 formed at the mouth. 



The supraorbital line, sup 0, is enclosed in a canal which 

 begins by a pore at the median border of the posterior nasal 

 opening, runs backward and inward toward the median line of 

 the head, where it anastomoses with its fellow of the opposite 

 side at a point in a transverse line drawn through the posterior 

 border of the lens of the eye. Here the canals diverge and 

 each runs to a point behind the eye a distance equal to half the 

 diameter of the latter. This canal opens at its ends only. 

 Five sense organs are found in the canal — three in the anterior 

 part and two in the posterior limb. 



The " frontal " group, fr, consists of two rows of organs. 

 It is located over the posterior end of the frontal bone, about 

 midway from the median line of the head to the outer edge of 

 its flat top. The outer row of each group consists of an aver- 

 age of six sense organs, with five phosphorescent organs, alter- 

 nating in a longitudinal row. The inner row is a shorter one, 

 parallel with the posterior part of the outer row, and consists 

 of from four to five sense organs with phosphorescent organs at 

 the inner and outer edge of each sense organ. The phospho- 

 rescent organs of this group, like those of other dorsal groups, 

 are especially variable in number and rudimentary. 



