246 planaxid^. 



Family PLANAXID^. 



Shell oval-conic, spire elevated, spirally striate ; columella 

 flattened, anteriorlj'^ 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. 



Planaxis, Lam. 



Distr. — 44 sp. West Indian, Indo-Pacific, Polynesian, Panamic. 

 P. sidcatus, Lam. (Ixix, 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. (Ixix, 45). 



QTjoYiA, 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 (Ixix, 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). 



Litiopa, Rang. 



Etym. — Litos^ simple ; ope, aperture. 



Distr. — 10 sp. Pelagic. Atlantic and Mediterranean, on 

 floating sea-weed, to which they adhere by threads. L. bombyx, 

 Rang (Ixix, 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 Anally becomes attached 

 to the weeds above. 



