480 MAifUAL OP THE MOLLTJSCA. 



impressions rounded, polished ; pallial sinus very large ; liga- 

 ment on shortest side of the shell, sometimes internal. Struc- 

 ture obscurely prismatic- cellular ; prisms fusiform, nearly 

 parallel with surface, radiating from the hinge in the outer 

 layer, transverse in the inner. 



Animal with the mantle widely open in front, its margins 

 fringed ; foot tongae-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 surface ; a few species inhabit estuaries 

 and rivers. Their valves are often richly coloured and orna- 

 mented with finely sculptured lines. 



Tellina, L. Tellen. 



Etymology, Telline, the Greek name for a kind of mussel. 



Synonyms, Peronsea [part) Poli. Phylloda (foliacea), Omala 

 (planata) Schumacher. Psammotea (solidula) Turt. Arco- 

 pagia (crassa) Leach. Tellinodora, Morch. 



Examples, T. Engua-felis, PL XXL, Fig. 5. T. carnaria, 

 I^ig. 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 ; pallial 

 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 other rudimental and directed dorsally. 



Tdlinides, Lamarck. T. planissima, PI. XXL, Pig. Y. Yalves 

 with no posterior fold ; lateral teeth wanting. 



T. carnaria {Strigilla, Turt.) has the valves obliquely sculp- 

 tured ; T. fahula, Gron. , has the right valve striated, the other 

 plain. T. Burneti, California, has the right valve flat ; T. lunu- 

 lata, Pliocene, South Carolina, much resembling it in shape, has 

 the left valve flat. 



Distribution, above 300 species. In all seas, especially the 

 Indian Ocean ; most abundant and highly coloured in the 

 tropics. Low water — Coral zone, 50 fathoms. Wellington 

 Channel ; Kara Sea ; Behring's Straits ; Baltic ; Black Sea. 



Fossil, 170 species. Oolites — . United States, South Am erica 

 (Chiloe), Europe. 



