A diagram of the interior right valve of genus Pinna (A) showing the position of the nacreous layer and 8 characteristics of the shell. 1 = total shell length (TSL); 2 = length of anterior to posterior adductor margin (LAPAM); 3 = posterior adductor to posterior shell margin (PAPSM); 4 = dorsal posterior shell margin (DPSM); 5 = dorsal margin (DM); 6 = shell width (ShW); 7 = sulcus width (SuW); 8 = posterior adductor margin to posterior nacreous margin (PAMPNM) and 9 = dorsal nacreous length (DNL). A diagram of the interior right valve of genus Atrina (B) showing the position of the nacreous layer and 8 characteristics of the shell. 1 = total shell length (TSL); 2 = length of anterior to posterior adductor margin (LAPAM); 3 = posterior adductor to posterior shell margin (PAPSM); 4 = dorsal posterior shell margin (DPSM); 5 = dorsal margin (DM); 6 = shell width (ShW); 7 = posterior adductor margin to posterior nacreous margin (PAMPNM); and 8 = dorsal nacreous length (DNL).

 
 
  Part of: Jela C, Monteclaro HM, Añasco NC, Quinitio GF, Babaran RP (2024) Identification of pen shells (Bivalvia: Ostreida: Pinnidae) collected off northern Iloilo, Philippines using their morphological characters. Acta Ichthyologica et Piscatoria 54: 49-61. https://doi.org/10.3897/aiep.54.112465