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            | Elongated toothed oyster Isognomon isognomum
 Family 
            Pteriidae
 updated 
            May 2020
 Where 
            seen? Like tongue depressors, these narrow long clams are 
            sometimes seen stuck upright to rocks and coral rubble near reefs.
 
 Features: 10-15cm. 
            The two-part shell is thick, flat and usually long and narrow, sometimes 
            with a T-shape near the bottom where it is stuck to a hard surface 
            with byssus threads. Usually dark, the shell is often coated with 
            encrusting organisms. Often found in groups of a few individuals stuck 
            in crevices.
 
 Sometimes confused with  Hammer oysters  that have a similar shape and also stuck upright 
            in crevices. It is difficult to tell them apart without ripping them 
            out of their hiding place and looking at the inside of the shell. 
            On the inside, Elonged toothed oysters have a long row of notches at the 
            hinge, and a large area of mother-of-pearl relative to the shell length.
 |  
        
          |  A large area of mother-of-pearl
 relative to shell length.
 Tanah Merah, 
          Dec 09
 |  A long row of notches at the hinge.
 |  Terumbu Semakau, 
          Nov 12
 |  
        
          |  Beting Bemban 
          Besar, Aug 12
 |  A long row of notches at the hinge.
 |  *Species are difficult 
      to positively identify without close examination.
 On this website, they are grouped by external features for convenience of 
      display.
 
 
        
          
            | Elongated toothed  oysters on Singapore shores |  
 
        
          
            | Other sightings on Singapore shores |  
 
        
          |  Terumbu Raya, Aug 21
 Photo shared by Vincent Choo on facebook.
 |  |  |  
 
         
          | Links             References 
                
              Tan Siong 
                Kiat and Henrietta P. M. Woo, 2010 Preliminary 
                Checklist of The Molluscs of Singapore (pdf), Raffles 
                Museum of Biodiversity Research, National University of Singapore. |  |  |