476 MANUAL OF THE MOLLTJSCA. 



Animal spinnitig a byssus ; foot thick, lanceolate, grooved ; 

 mantle plain or finely fringed ; freely open in front ; siphons 

 moderate, separate half-way or throughout, orifices fringed, 

 anal cirri simple, branchial ramose ; palpi long, triangular. 



Distribution, 78 species. Norway, Britain, Black Sea, Senegal, 

 Brazil, India, China, New Zealand. Low water — 100 fathoms. 

 (Beechy.) 



Fossil, 6 species. Pliocene — . Britain, France, Belgium, 

 Italy. 



The animal is eaten on the continental coasts ; it buries in 

 the sand at low water, or hides in the crevices of rocks, and 

 roots of sea-weed. 



Yenertjpis, Lamarck. 



Etymology, Venus, and rupes, a rock. 



Synonym, Gastrana, Schum. 



Example, Y. exotica, PI. XX., Fig. 15. 



Shell oblong, a little gaping posteriorly, radiately striated 

 and ornamented with concentric lamelloe ; three small teeth in 

 each valve ; one of them bifid ; pallial sinus moderately deep, 

 angular. 



A7iimal with the mantle closed in front, pedal opening mode- 

 rate; siphons united half-way, and with a simple fringe and 

 tubular valve, branchial siphon doubly fringed, inner cirri 

 branching ; palpi small and pointed. 



Distribution, 19 species. Britain — Crimea ; Canaries, India, 

 Tasmania, Kamtschatka, Behring's Straits — Peru. In crevices 

 of rocks. 



Fossil, Miocene — . United States, Europe. 



Petricola, Lamarck. 



Etymology , petra, stone, colo, to inhabit. 



Synonyms, Bupellaria, Bellevue ; Choristodon, Jonas ; Na-? 

 ranio. Gray. 



Tij];)e, P. lithophaga, PI. XX.,. Fig. 16. P. pholadiformis, 

 PI. XX., Fig. 17. 



Shell oval or elongated, thin, tumid, anterior side short; 

 hinge with 3 teeth in each valve, the external often obsolete ; 

 pallial sinus deep. 



Animal with the mantle closed in front, much thickened and 

 recurved over the edges of the shell ; pedal opening small ; 

 foot small, pointed, lanceolate; sii-)hons partially separate, 

 orifices fringed, anal with a valve and simple cirri, branchial 

 cirri pinnate ; pal])! small, triangular. 



