Main Ref.	Sabelli, B. and H.S. Feinberg (eds.), 1879
Appearance refers to

Sex attributes

specialized organs
different appearance
different colors
remarks

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth
Diagnosis	Shell: convex valves, slightly inequivalved and inequilateral; coloration is cream or delicately pink; sculpture consists of a score of radialribs decorated with spines whose breadth progressively increases from the umbo to the ventral margin of the valve; between the ribs are small granulations, irregularly arranged; lunule is very differentiated and heart-shaped; ligament is external, hinge is pachyodont; two large muscle scars (posterior is bigger than the anterior; dimyarian, anisomyarian), pallial line is continuous with no sinus. Body: foot is reduced to keep with its sedentary life; mantle cavity has a pair of gills, each with two series of lamellae, extensively fused by interlamellar junctions (eulamellibranch).
Ease of Identification

Meristic characteristics of Arcinella arcinella

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

Fins

Dorsal fin(s)

Attributes
Fins number
Finlets No.	Dorsal
	Ventral
Spines total
Soft-rays total
Adipose fin

Caudal fin

Attributes

Anal fin(s)

Fins number
Spines total
Soft-rays total

Paired fins

Pectoral	Attributes
	spines
	soft-rays
Pelvics	Attributes
	Position
	spines
	soft-rays