CONCHIFERxV. 317 



Fig. 220. Mya truncata, L. |. Brit, (after Forbes.) 



Mya, L. Gaper. 



Etym. Mijax (-acis) a mussel, Pliny. Stjn. Platyodon, Conrad. 



Tijpes, M. truncata, PI. XXIII. fig. 1. M. Arenaria, fig. 170, p. 244. 



Shell oblong, inequivalve, gaping at the ends ; left valve smallest, with a 

 large flattened cartilage process ; pallial sinus large. 



Animal with a small straight linguiform foot ; siphons combined, covered 

 with epidermis, partially retractile ; orifices fringed, the branchial opening 

 with an inner series of large tentacular filaments ; gills not prolonged into 

 the siphon ; palpi elongated, free. 



M. anaihia, Chemn. (Tugonia, Gray) W. coast of Africa ; posterior side 

 extremely truncated; similar cartilage-processes in each valve. Fossil, 

 Miocene, Das, and the Morea, 



Distr. 10 sp. Northern Seas, W. Africa, Philippines, Australia, Cali- 

 fornia. The Myas frequent soft bottoms, especially the sandy and gravelly 

 mud of river-mouths ; they range from low-water to 25 fathoms, rarely to 

 100 or 145 fms. M. arenaria burrows a foot deep ; this species and M, 

 truncata are found throughout the northern and Arctic seas, from Ochotsk 

 and Sitka to the Russian Ice-meer, the Baltic, and British coast ; in the 

 Mediterranean they are only found fossil. They are eaten in Zetland and 

 N. America, and are excellent articles of food. In Greenland they are sought 

 after by the walrus, the Arctic fox, and birds. {0. Fabriciiis) 



Fossil, Miocene — . U. States, Brit. Sicily. Most of the fossil 

 "Myas" have an external ligament, and are related either to P^^wo^jt^ap or 

 Fholadomya. 



CoRBULA, Bruguiere. 



Etym. Corbula, a little basket. Type, C. sulcata, PI. XXIII. fig. 2. 



Syn. Erodona, Daud. (= Pacyodon, Beck.) Agina, Turt. 



Shell thick, inequivalve, gibbose, closed, produced posteriorly; right 

 valve with a prominent tooth in front of the cartilage pit ; left valve smaller, 

 with a projecting cartilage process ; paUial sinus slight : pedal scars distinct 

 from the adductor impressions. 



Anirnal with very short, united siphons ; orifices fringed ; anal valve 

 tubular ; foot thick and pointed ; palpi moderate ; gills 2 on each side, ob- 

 scurely striated. 



