40 GASTROPTERON. 
the head-disk, foot and wings are purple, orange-red or rose, more or 
less maculated with whitish, head-disk and wings white-edged, sole 
paler, and mantle with a posterior filament. 
G. pacificum Bergh, of the Aleutian Is., which is pale yellow 
flecked with reddish throughout, the mantle with no filament or 
flagellum behind, and 
G. sinense A. Ad., which has not yet been adequately described, 
but seems nearest to G. rubrum. 
G. RUBRUM Rafinesque. PI. 7, figs. 1-10; pl. 8, figs. 11, 12, 13, 16. 
General color varying from red-purple to pale rose, sometimes 
with some spots of bluish-white; on the periphery of the head-disk 
and the parapodia there is an iridescent blue border. The ventral 
surface of the foot proper is always paler in color than the rest of 
the body. Mantle having a posterior filament. Jaws small. Rad- 
ula with the formula 5:1:0°1°5. Shell nautiloid, microscopic, cal- 
careous and very hyaline. 
Length, 20-24; breadth, 25-30 mill., or smaller. 
Mediterranean, Afgean and Adriatic Seas; Archachon basin, Gi- 
ronde, 50-120 meters. 
Gastropteron KossE, De pteropodum ordine et novo 
ipsius genera, 1813, p. 10-16, figs. 11-14.—Sarcopterus ruber RAFIN- 
ESQUE, Quadro dei generi di Moll. Pteropodi, in Specchio delle Sci., 
ii, p. 11, Nov. 1814; Précis des découvertes somiologiques ou Zool- 
ogiques et Botaniques, p. 30 (1814).—G. meckeli BLAtNvILLE, 
Manual de Mal. et Conch., p. 479 (1825).—Puxt., Enum. Moll: 
Sicil., 1, p. 124.—Sou.eyet, Voy. Bonite, Zool., ii, p. 464, pl. 26.— 
Krouy, Archiv f. Naturg., 1860, p. 64, pl. 2, f. 2, 3 (larva and 
shell).—VayssrerE, Ann. Se. Nat., Zool. (6) ix, p. 1-72, pl. 1-6; 
Rech. Moll. Opistobr., Ire Pt., Tectibranches, p. 40, figs. 835-41.— 
Berau, Zool. Jahrb., vii, p. 281-303, pl. 16, f. 1-27, pl. 17, f. 1-10- 
—Gastropteron rubrum FiscHER, Journ. de Conchyl., 1890, p. 349. 
—Gasteropteron coccineum FERussAc, Tabl. Syst. p. 25.— Clio amatt 
De.Le Curase, Mem. sulla Storia e Notomia degli Anim. senza 
Vert., 1, p. 53-59, pl. 2, f. 1-8 (1823). 
The shell-cavity of the mantle is very large, occupied throughout 
its extent by a delicate, very hyaline membrane, at the posterior 
part of which is found the small nautiloid shell (pl. 7, fig. 4). The 
shell is nautiliform, hyaline and translucent, resembling in texture 
