PLANAXID.K. 237 



Genus ATRESIUS, Gabb, 1869. 

 Elongated, spire elevated, whorls rounded ; aperture ovate, 

 slightly produced in front, outer lip entire, thin, columella not cal- 

 lous ; imperforate ; surface marked by spiral ribs. A. liratus, 

 Gabb. Cretaceous. 



California. 

 Possibly belongs in Cerithiidse. 



No recent illustrated monograph of Fossaridse has been pub- 

 lished. Dr. Fischer printed a systematic Catalogue of the Species, 

 with synonymy, in ''Journal de Conchyliologie," for 1864. 



Family PLANAXIDjE. 



Shell oval conic, spire elevated, without varices ; columella flat- 

 tened, truncate anteriorly, lip rounded, simple, notched in front. 

 Operculum corneous, subspiral. 



Animal with rather long rostrum, subulate tentacles and eyes 

 on swellings at their base. 



^ The Planaxidse have been monographed by Sowerby, in Con- 

 chologia Iconica, xx. 



Subfamily Flanaxin.15. 

 Siphon very short, foot simple. Shell spirally grooved. Den- 

 tition (PI. 40,"^ fig. 69.) 



Subfamily LiTioPiNyE. 

 Animal (PI. 40, %. 79.) No siphon, foot with three cirriform 

 filaments, operculigerous lobe with two posterior filaments. Denti- 

 tion (PI. 40, fig. 70.) Shell minute, thin, smooth, plicate or 

 spirally striate. 



Planaxince. 



Genus PLANAXIS, Lamarck, 1822. 



Shell imperforate, oval-conic, solid, with epidermis, and elevated 

 spire, usually spirally sulcate ; columella callous, flattened, truncate 

 at base, with a narrow sinus ; interior of aperture ridged, base 

 notched. Operculum paucispiral, with a nearly terminal nucleus. 



Amphibious, crawling on stones near the margins of pools left by 

 the retiring tide, or adhering to mangrove roots. About fifty 

 species are known, tropical or subtropical. Fossil ; pliocene of the 

 West Indies. P. sulcatus, Born. 



