| Main Ref. | Sabelli, B. and H.S. Feinberg (eds.), 1879 |
| Appearance refers to |
| specialized organs | |
| different appearance | |
| different colors | |
| remarks |
| Striking features | |
| Body shape lateral | |
| Cross section | |
| Dorsal head profile | |
| Type of eyes | |
| Type of mouth/snout | |
| Position of mouth | |
| Diagnosis | Shell: solid, moderately convex valves equivalved and almost equilateral, circular or oval in shape, umbones frequently eroded; thick yellowish periostracum in young individuals, darkish brown to blackish in adults; cream-colored shell; sculpture consists of incised concentric lines sometimes toward the umbo, slightly raised ribs; external ligament takes over half the area posterior to the umbones; heterodont hinge, two cardinal teeth on the right valve and three on the left; smooth outer valve margin; two equal muscle scars (dimyarian, isomyarian) joined by a continuous pallial line (integropaliiate) without a sinus; crossed-lamellae structure. Body: pair of gills each has two series of lamellae extensively fused by interlamellar junctions (eulamellibranch); moderately developed foot. |
| Ease of Identification |
| Lateral Lines | Interrupted: No |
| Scales on lateral line | |
| Pored lateral line scales | |
| Scales in lateral series | |
| Scale rows above lateral line | |
| Scale rows below lateral line | |
| Scales around caudal peduncle | |
| Barbels | |
| Gill clefts (sharks/rays only) | |
| Gill rakers | |
| on lower limb | |
| on upper limb | |
| total | |
| Vertebrae | |
| preanal | |
| total |
| Attributes | |
| Fins number | |
| Finlets No. | Dorsal |
| Ventral | |
| Spines total | |
| Soft-rays total | |
| Adipose fin |
| Attributes |
| Fins number | |
| Spines total | |
| Soft-rays total |
| Pectoral | Attributes |
| spines | |
| soft-rays | |
| Pelvics | Attributes |
| Position | |
| spines | |
| soft-rays |