EXPLORATION OF ALASKA. 259 
The oral tube whitish, of about 1.0 mm. length, wide. The bulbus 
pharyngeus clear brownish-yellow, somewhat pyriform, with oblique 
flattened posterior end, in length about 1.6, by a height of nearly 1.3, 
and a breadth of 1.5 mm.; the sheath of the radula a little prominent 
downwards, and to the left from the hindermost part of the under side of 
the bulbus. The lip-disk clothed with a brownish-yellow cuticula, that 
is continued into the two mandibular plates behind the lip-disk at the 
entrance of the oral cavity, the form of the mandible could not be 
determined with certainty ; a yellowish cuticula clothes the rest of the 
cavity. The tongue with ten rows of plates, further backwards six 
developed and two younger rows; the total number eighteen.! The 
rhachis (fig. 2) not very narrow. The plates yellow. The length of 
the first plate about 0.11, of the second 0.20, of the inmost of the ex- 
ternal plates 0.14, of the following 0.12, 0.10, 0 08 and 0.06 mm. (all 
from the hinder part of the sheath). The first lateral plate (fig. 2aa, 
5, 6) formed somewhat as in the P. Lessouzi, the hook still smaller ; 
the second of the same form, but larger (fig. 265, 3), the hooks much 
larger, especially the anterior, which is broader and excavated (fig. 7). 
More outwards five external plates (fig. 2cc), all with a crest, which is 
larger in the two innermost; adjoining the outermost of these plates 
several longitudinal folds of the lingual cuticula, which sometimes 
simulate one to two plates more (fig. 2). 
The salivary glands whitish, elongate. The cesophagus rather wide, 
the stomach inclosed in the liver. ‘The intestine appearing at the 
middle of the length of the liver a little to the left, at the bottom of a 
deep and large cavity in the upper side of the liver; the pyloric part 
1 According to Alder and Hancock (Monog. Part VII, 1855, Pl, 41 sup- 
plement, fig. 20, 21), the number of rows was fifteen in the Polycera quad- 
rilineata, sixteen in the P. ocellata, thirteen in the P. Lessonii ; Alder and 
Hancock saw (1. c.) four external plates in the Pol. quadrilineata, five in 
P. ocellata, and six in P. Lessonit. Meyer and Moebius saw five to seven 
external plates in their Polycera ocellata, whilst the number of rows (1. ¢. 
Pl. 50) is noted as thirteen to fifteen; in the P. quadrilineata they found 
four to five external plates and twelve to thirteen rows. In four specimens 
of Pol. quadrilineata I saw six to eight rows on the tongue, more back- 
wards six to seven developed, and one not quite developed row ; the total 
number of rows was fourteen to fifteen. In all specimens there were but 
four external plates. In four specimens of Pol. Lessonii I saw nine to ten 
rows on the tongue, more backwards eight to seven or five developed, 
and a single not developed row; the total number of rows was sixteen to 
eighteen. In all the specimens there were eight external plates. 
