MONOGRAPH OF THE GENUS 



TAPES. 



Fam. Veneridse. 



(Tapes, Megerle; Pullastra, Sowerh^.) 



Char. Gen. Testa sequivalvis, insequilateralis, plerumqne ovali- 

 oblonga, plerumque concentrice plus minusve lirata. Cardo elon- 

 gatus, angustatus, deutibus in utraque valva tribus, compressis, 

 posticis et medianis duplicatis. Ligamentum elongatom. Im- 

 pressiones musculares pyriformes. Impressio pallii sinu profundo, 

 plerumque elongato. 



The distinctions between these shells and those of the genus 

 Venus are vague and uncertain; consisting principally in the 

 lengthened form of outline, and in the compressed and bifid cha- 

 racter of the hinge-teeth. The sinus in the pallial impression is 

 also generally deep and conformed to the length of the shell. 

 The external surface is generally marked by concentric ribs or 

 strise. The typical species, Venus pnllnstra, and its rock-dwelling 

 variety V. perforans, have been placed in separate genera (the 

 latter in Venerirupis, Lamarck), but are now established beyond 

 question as belonging to the same species ; the difference of form 

 and surface resulting from the accidental confinement of the shell in 

 some small hollow preventing its full development. Tapes decussata 

 leads into several other species which have radiating strise or ribs ; 

 and these again lead into others wliich so nearly resemble them 

 as to induce me to include them, although they have crenulated 

 inner margins. Although some of the species are subject to 

 occasional confinement in small hollows of rocks, it is by no 

 means the general habit of the genus, as in the case of the true 

 Venerin(p)es. 



Many of the large and finely coloured species of Tapes are 

 inhabitants of the Australasian seas, while others of less striking 

 development are found near the British coasts and in the Medi- 

 terranean. 



