No. 3.] LATERAL LINE OF AMIA. 493 
openings, all in the nasal, and all belonging to group 6 infra- 
orbital. 
Groups 5 and 6 are almost always continuous, both lying be- 
tween the eyes on top of the head, No. 5 almost directly behind 
the posterior nasal aperture, and No. 6 much nearer the middle 
line of the head, and extending somewhat behind the eye. In 
the 17-inch specimen there were in these two groups one hun- 
dred and nine pores; in the 20}-inch one, one hundred and six- 
teen, and in the skull eighty-two openings. In the 27-inch 
specimen these groups were continuous with 3 and 4 supra- 
orbital and 6 infra-orbital. The total number of pores in the 
five groups in this specimen was three hundred and fifty-four ; 
in the 17-inch one, one hundred and fifty-six, and in the 20}- 
inch one, one hundred and seventy-four. 
Group 8 lies behind group 6, not so near the middle line of 
the head, and about half way between that group and the supra- 
temporal cross-commissure. It had in the 17-inch specimen 
twenty-nine pores; in the 20}-inch one, thirty-two; in the 27- 
inch one, ninety-three ; and in the skull, seventeen openings. 
4. Operculo-mandibular Line. — Group 1 of the operculo-man- 
dibular line in all the numerous specimens examined, excepting 
only the unusually large 27-inch one, had only a single large 
pore belonging to it; the two pores, one on each side, lying 
directly in front of the gular plate, near the tip of the lower 
jaw and close to its middle line. In the 27-inch specimen there 
were two pores on each side of the head, lying in a line trans- 
verse to the direction of the trunk of the system as seen from 
below. 
The pores of group 2 and those of the succeeding groups to 
No. 10 are arranged in regular lines, approximately parallel to the 
inner edge of the mandible, but the lines of the different groups 
are broken, and overlap, or are continuous with each other, so 
that the number of pores belonging to each cannot be deter- 
mined. In groups I to 10 inclusive, in the 17-inch specimen, 
there were sixty-six pores; in the 20}-inch one, seventy-two ; 
and in the 27-inch one, one hundred and twenty-five. In the 
skull there were seventy-four openings, many of them double. 
Group 11 lies at the hind end of the mandible, in front of and 
above group 10, and about half way between the maxilla and 
the lower end of the pre-opercular fold. It lies on both sides 
