42 GASTROPTERON. 
regarding the genus as a Pteropod, for, at first sight, it has all the 
appearance and action of a Pneumodermon. My specimens ap- 
peared to want the power of crawling altogether; the animals, 
after taking short flights, usually upside down, through the water, 
by butterfly flappings of the side-lobes of the foot, gently alighted 
and remained stationary on their stomachs, with the swimming- 
lobes folded together over the back, until ready for another little 
excursion. The lower surface of this species, moreover, is colored 
exactly like the fins, and shows no signs of a creeping disk. I be- 
lieve the genus should be placed in the family Lophocercide, or 
rather, Icaride; for Prof. E. Forbes had _ previously described 
Lophocercus under the name of Icarus. The Chinese species seems 
to differ from the Mediterranean Gasteropteron in being covered 
with crimson punctate and reticulate markings. Other points of 
difference are shown in my drawings. (Ad.). 
G. paciFicuM Bergh. PI. 8, figs. 14, 15, 17-23. 
Living animal yellowish, flecked with red. Margin of mantle 
without a flagellum. General proportions as in G. rubrum, but. 
smaller; foot usually distinctly demarked from pleuropodial lobes, 
which are smaller and a little shorter. Free margin of the mantle 
narrower, Only behind a little wider, but without trace of filament. 
On account of the narrowness of the mantle-skirt, the gill is nearly 
exposed, relatively larger than in G. rubrum, directed more down- 
ward ; leaflets of gill fewer, 16-20, and free ends of the same longer ; 
the black kidney-pore is nearer the anus. Genital openings and 
semen-groove as in rubrum. ‘The shell (pl. 8, fig. 18) is as in rub- 
rum, the calcified portion measuring “6 to ‘66 mill., chalk-white, 
radially striate, and very fragile, the large cuticular last whorl 
(fig. 19) as in G. rubrum. Dentition (pl. 8, fig. 21) as in G. rubrum, 
formula 5:1:0°1°5 or 6°1:0°1°6 ; laterals (pl. 8, figs. 20, 22) and uncini 
(pl. 8, figs. 21, 23) offering no especial differential features. 
Unalaschka, Aleutian Is., 9-15 fms (Dall.). 
G. pacificum Bereu, Zool. Jahrb. vii, p. 3038, pl. 16, f. 28; pl. 17, 
f. 10-26 (1893). Bull. Mus. Comp. Zool., xxv, p. 202, pl. xii, f. 1-2. 
Specimens preserved in alcohol still retained part of the original 
coloration, the head-shield, foot and pleuropodia clear yellowish, 
with numerous red dots, more or less grouped and more or less close ; 
on the under side and free apex of head-shield they were closer. 
The posterior body gray, usually, especially in front, strewn with red- 
