Atlanta peronii is the type species in the genus Atlanta. It attains the largest size of all atlantids (to 10 mm shell diameter). The walls of the shell are unusually thick and strong. The keel is moderately tall and rounded in side profile, with a slightly truncated leading edge. The keel base is clear in young animals, but changes with age to a light brown and then a dark yellowish-brown. The keel inserts between the fourth and fifth whorls in shells larger than about 3 mm. The spire consists of 3-1/2 to 3-3/4 whorls. The whorl surfaces are smooth. The sutures between the first and second whorls are shallow, while those between subsequent whorls are incised. Full grown shells can consist of up to 6 whorls. Shell transparent, but can become faintly yellow in large individuals. Eyes type b. Operculum type b. Radula type II, large with sexually-dimorphic marginal teeth. The species is cosmopolitan in tropical to subtropical waters. In Hawaiian waters, A. peronii is a strong nocturnal vertical migrator, ranging downward to a daytime maximum of 300 m and migrated into the upper 150 m at night.

Diagnosis

• Maximal shell diameter = 10 mm
• Shell with thick, strong walls, consisting of up to 6 whorls
  
• Shell transparent, but becomes a faint yellow in older animals
• Keel moderately tall and rounded, inserting between fourth and fifth whorls in shells larger than about 3 mm
  
• Keel base clear in young individuals, becoming brown to yellow-brown with age
• Spire consists of 3-1/2 to 3-3/4 whorls
• Sutures between the first and second whorls shallow; subsequent sutures incised
  
• Spire whorls smooth
• Eyes type b
• Operculum type b
• Radula type II; large, with sexually-dimorphic marinal teeth