EXPLORATION OF ALASKA. 263 
breadth of 5.56 mm.; the height of the branchial leaves 1.25, of 
the rhinophoria 2.0 mm. ; the breadth of the foot 3.5 mm. 
The form as usual. The head flattened in front, semilunar ; 
the tentacles compressed-cup-shaped, rather short (about 1.0 mm. 
long), truncated at the end, longitudinally folded and open at 
the outer side. The frontal margin not projecting much, with 
many smaller and larger short digitations and crenulations; in 
front in the median line were two small conical papillz before 
the region of the rhinophoria. The margin of the rhinophor- 
holes somewhat projecting, smooth: the (deeply retracted) rhino- 
phoria with rather short stalk; the club with thirty-five to forty 
rather broad and thin leaves. 
The back rounded over from side to side, without certain limits 
between it and the sides of the body. At the lateral parts 
of the back (on each side) five appendices; the first standing a 
little behind the end of the frontal margin; the next about in 
the middle of the space between the first and third; this last a 
little before the region of the gill; farther backwards were also 
two similar ones. The appendices were club-shaped, with simple 
or composite nodosities spread upon their bodies, and especially 
at their bases; the third was the largest, reaching the height of 
about 2.5 mm.; all the others a little smaller, and all of about 
the same size. Much smaller, conical or club-formed simple 
papille were scantily and irregularly scattered on the back. The 
gill consisting of five strong, tripinnate, quite separate leaves, a 
single anterior and two lateral pairs. The anal nipple nearly 
in the centre of the posteriorly open branchial circle, a blunted, 
nearly cylindrical prominence, about 0.5 mm. in height; at its 
base on the right side and a little forwards was the very distinct 
renal pore. The sides of the body rather high and smooth; the 
genital opening a short longitudinal slit lying rather forwards, 
with two openings at its bottom. The foot not very narrow, of 
nearly the same breadth throughout its whole length ; the anterior 
border emarginated in the middle, with a fine line. 
The intestines did not shine through the integuments. The 
peritoneum was colorless, without spicula. 
The central nervous system (Pl. XV, fig. 1) flattened; the 
cerebro-visceral ganglia (fig. la) reniform, a little narrower at 
the fore-end ; the pedal ones (fig. 1bb) rounded, scarcely larger 
than the visceral; the large commissure (fig. 1) as usual; small 
