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 Lophocercidse, or 

 rather, IcaridsB; 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 (pi. 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 (pi. 8, fig. 21) as in G. rubrum , 

 formula 5-l'0'l'5 or 6'1'0-1'6 ; laterals (pi. 8, figs. 20, 22) and uncini 

 (pi. 8, figs. 21, 23) offering no especial differential features. 



Unalaschka, Aleutian Is., 9-15 fms (Dall.). 



G. pacificum BERGH, Zool. Jahrb. vii, p. 303, pi. 16, f. 28 ; pi. 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 ; 

 v on the under side and free apex of head-shield they were closer. 

 The posterior body gray, usually, especially in front, strewn with red- 



