310 MANUAL OF THE MOLLUSCA. 



Animal with the mantle widely open in front, its margins fringed ; foot 

 tongue-shaped, compressed ; siphons separate, very long and slender ; palpi 

 large, triangular ; gills united posteriorly, unequal, the outer pair sometimes 

 directed dorsally. 



The Tellens are found in all seas, chiefly in the littoral and laminarian 

 zones ; they frequent sandy bottoms, or sandy mud, burying beneath the sur- 

 face ; a few species inhabit estuaries and rivers. Their valves are often richly 

 coloured and ornamented with finely sculptured lines. 



TELLINA, L. Tellen. 



Etym. Tel line, the Greek name for a kind of mussel. 



Syn. Peroneea (part) Poli. Phylloda (foliacea), Omala (planata) Schum. 

 Psammotea (solid ula) Turt. Arcopagia (crassa) Leach. 



Examples, T. lingua-felis, PI. XXT. fig. 5. T. carnaria, fig. 6. 



Shell slightly inequivalve, compressed, rounded in front, angular and 

 slightly folded posteriorly, umbones sub-central ; teeth 2.2, laterals 1 1, 

 most distinct in the right valve ; pallia! sinus very wide and deep ; ligament 

 external, prominent. 



Animal with slender, diverging siphons, twice as long as the shell, their 

 orifices plain ; foot broad, pointed, compressed ; palpi very large, triangular ; 

 gills small, soft and very minutely striated, the outer rudimental and directed 

 dorsally. 



Tehimdes, Lam. T. planissima, PI. XXI. fig. 7. Valves with no pos- 

 terior fold ; lateral teeth wanting. 



T. carnaria (Striyilla, Turt.) has the valves obliquely sculptured ; T.fa- 

 bula, Gron. has the right valve striated, the other plain. T, Burnett, Cali- 

 fornia, has the right valve flat ; T. hinulata, Pliocene, S. Carolina, much 

 resembling it in shape, has the left valve flat. 



Distr. above 200 sp. In all seas, especially the Indian Ocean ; most 

 abundant and highly coloured in the tropics. Low-water Coral zone, 50 

 fins. AY ellington Channel; Kara Sea; Behrings' Sea ; Baltic: Black Sea. 

 Fossil, 130 sp. Oolites . U. States, S. America (Chiloe) Europe. 



DIODONTA, Schumacher. 



Etym. Di- two, odonta teeth. Syn. Fragilia, Desh, 



Type, Tellina fragilis, L. PI. XXI. fig. 8. 



Shell equivalve, convex, with squamose lines of growth ; cardinal teeth 

 2 in right valve, 1 bifid tooth in left ; pallial sinus deep and rounded ; um- 

 bonal area punctate ; ligament external. 



Animal with the mantle open in front, its margins fringed; siphons 

 elongated, slender, separate, unequal, orifices with cirri ; foot small, com- 

 pressed, linguiform ; palpi large, triangular ; gills unequal, soft, finely striated. 



Diodonta inhabits shallow water, boring in mud and clay, and not travel- 

 ling about like the Tellens. 



