246 PLANAXIDA. 
Famity PLANAXIDA. 
Shell oval-conic, spire elevated, spirally striate; columella 
flattened, anteriorly truncate; lip rounded, simple, notched in 
front. Operculum corneous, subspiral. 
Animal with a rather long rostrum, subulate tentacles, and eyes 
on swellings at their base, foot short, plain in Planaxis, with 
tentacular filaments in Litiopa. 
PLANAXxIsS, Lam. 
Distr.—44sp. West Indian, Indo-Pacific, Polynesian, Panamic. 
P. sulcatus, Lam, (xix, 44). Fossil. Tertiary. 
Shell oval-conic, solid, with elevated spire; usually spirally 
ribbed ; columella callous, flattened, truncate at base, with a 
narrow sinus; interior of aperture ridged; base notched. 
Amphibious, crawling on stones near the margins of pools left 
dry by the retiring tide. Some of the species inhabit mangrove 
swamps, and may be seen adhering to the roots above the surface 
of the water. 
HINEA, Gray. Shell smooth, covered by a yellowish brown 
epidermis ; whorls flattened, outer lip thick, sillonated within. 
P. Braziliana, Lam. (1xix, 45). 
quoy1A, Desh. (Fissilabra, Brown. Leucostoma, Swains.) 
Shell solid, elongated, whorls flattened, spirally striated, apex 
decollated ; mouth small, slightly notched in front, sillonated 
within; columella smooth, truncate anteriorly, with a sharp spiral 
posterior callus. P. decollata, Quoy (lxix, 46). 
HOLcosToMA, H. and A. Adams. Shell thin, aperture furnished 
with a posterior canal which extends up the last whorl; it is 
covered with an epidermis curiously adorned with rows of golden 
bristles. P. piligerum, Phil. (Ixix, 47). 
Liriopa, Rang. 
Ktym.—Litos, simple ; ope, aperture. 
Distr.—10 sp. Pelagic. Atlantic and Mediterranean, on 
floating sea-weed, to which they adhere by threads. L. bombyx, 
Rang (lxix, 48). Fossil. Tertiary. 
Shell minute, pointed; aperture slightly notched in front ; 
outer lip simple, thin; inner lip reflected ; operculum spiral. 
The singular little oceanic mollusks which constitute this 
genus have the power of spinning glutinous threads by which 
they occasionally suspend themselves from the stems of floating 
sea-weed, among which they take up their abode; if the thread 
by any chance becomes divided, the animal emits a bubble 
enveloped in a glutinous secretion, which rises to the surface, 
drawing out threads as it ascends, and finally becomes attached 
to the weeds above. 
