▁attached ▁to ▁slow - mov ing ▁sub mer ged ▁objects ▁or ▁organ isms . ▁All ▁species ▁of ▁Mol g ula ▁have ▁a ▁fluid - filled ▁structure ▁called ▁the ▁ren al ▁sac . ▁The ▁ren al ▁sac ▁contains ▁nit ro gen ous ▁was tes , ▁solid ▁con cret ions ▁composed ▁of ▁wed d ellite ▁and ▁cal cite , ▁and ▁an ▁ap ic om plex an ▁sym b ion t ▁called ▁Ne ph rom y ces . ▁ ▁In ▁the ▁western ▁Atlantic ▁Ocean , ▁they ▁range ▁from ▁the ▁Ar ctic ▁to ▁North ▁Carolina , ▁to ▁the ▁center ▁of ▁the ▁United ▁States ▁Eastern ▁Se ab o ard . ▁ ▁Species ▁▁ ▁Mol g ula ▁a idae ▁O ka , ▁ 1 9 1 4 ▁ ▁Mol g ula ▁am es oph le ba ▁( C od re anu ▁& ▁Mack - F ira , ▁ 1 9 5 6 ) ▁ ▁Mol g ula ▁ant ib ore alis ▁Mill ar , ▁ 1 9 6 7 ▁ ▁Mol g ula ▁append icul ata ▁H eller , ▁ 1 8 7 7 ▁ ▁Mol g ula ▁aren ata ▁Stim pson , ▁ 1 8 5 2 ▁ ▁Mol g ula ▁b ac ca ▁( H erd man , ▁ 1 9 1 0 ) ▁ ▁Mol g ula ▁bath y bia ▁( H art me yer , ▁ 1 9 1 2 ) ▁ ▁Mol g ula ▁bis inus ▁Mon ni ot , ▁ 1 9 8 9 ▁ ▁Mol g ula ▁ble izi ▁( L ac