348 SAXICAVIDiE. 



constricta, Lam. olivacea, Metcalfe. 



Gangetica, Bens. rufa, Bosc. 



Fam. SAXICAVIDJE. 



Animal symmetrical, oblong. Mantle-lobes united and 

 thickened in front ; siphons large, elongated, often invested 

 with a thick, wrinkled epidermis, united nearly to their ends, 

 the orifices fringed; pedal opening small; gills two on each 

 side, narrow, unequal, united behind, and extending into 

 the branchial siphon. Foot small, digitiform, inferior, 

 furnished with a byssal groove. 



Shell equivalve, solid, gaping at each end ; hinge-teeth 

 rudimentary; cartilage external, thick, prominent. Pallial 

 impression irregular, sinuated posteriorly. 



Perforating stones, or living imbedded in sand and mud, 

 but not enclosed in shelly cases or protecting tubes. 



The Saxicavidce approach in many respects the Gastro- 

 cluenidce, but, though often perforating stones, they do not 

 form shelly cases or protecting tubes. In their closed mantle 

 and extended, united siphons they likewise resemble the 

 Myiche, but their gills extend into the branchial siphon, their 

 body is symmetrical, their foot is furnished with a byssal 

 groove, and their shell is equivalve, with the cartilage 

 external. 



Genus SAXICAVA, Fleuriau de Bellevue. 



Palpi small, free; siphons large, united nearly to their 

 ends, orifices fringed. 



Shell oblong, equivalve, valves rugose, gaping, beaks pro- 

 minent. Hinge, when young, with two small teeth in each 



