Atlanta californiensis Seapy and Richter, 1993
Overview
This is a flat transparent calcareous keeled snail, about 0.3 cm in diameter. The spire is low and globular with 4.5 whorls. The suture is shallow, the umbilicus is deep and wide. It is epipelagic in the eastern tropical Pacific.
Taxonomic Description [after original description]
Shell moderately small, with 4.6 whorls. The keel penetrates between last and penultimate whorl in shells greater than 2 mm in diameter (Atlanta californiensis). Keel base is orange-brown to red-brown. The spire is low conical to globular in profile view and surface sculpture is lacking (Atlanta californiensis tip). The spire is light yellow, brown or violet or it shows a light to dark mottled pattern of yellow-brown to brown. The suture is violet to purple. The umbilicus is wide, but narrows rapidly with the penultimate whorls divided internally by a thin, flexible chitinous membrane. Larval metamorphosis occurs at a shell diameter of 0.5-0.6 mm. The operculum, type C, is thin transparent and oval with a monogyre nucleus. There are no spiral lines with spines. The eyes of the type A, In this species t relatively small. The dorsal window is triangular. The Atlanta californiensis radula formula 2-1-1-1-2 is large, elongate and narrowly triangular. There is sexual dimorphism in the radula, the growth angle is 20-22°: in males length is up to 1000 µm, width up to 260 µm with 99 transverse rows, the central tooth with low broad base, is unicuspoid with short cusp; lateral teeth have a very broad curved basal plate, and one strong cusp; inner and outer addition teeth of equal size, slender, curved at the tip and smaller than the laterals; in females the length is up to 700 µm maximum width 170 µm, growth angle 17-18°, number of rows 62; the basal plate of central and laterals is narrower than in males and the additional and lateral teeth are shorter than in males.
Shell diameter up to 3.5 mm.
Juveniles
The juveniles have a small dextrally coiled shell. A special description is not available. A young specimens is given in the figure (Atlanta californiensis young).
Reproduction
In this species the sexes are separate.
Ecology
This species is carnivorous and epipelagic. Males occur in great numbers in the neuston.
Distribution
Tropical East Pacific, Transitional zone waters, see the Atlanta californiensis map.
Types
Atlanta californiensis Seapy and Richter, 1993: 398.
Holotype: adult female mounted on SEM stub SBMNH 140126. Paratype adult male mounted in SEM stub SBMNH 140127. All types preserved in Santa Barbara Museum of Natural History.
Type locality: Santa Catalina Basin, 33°03.4'N 118°24.7'W, 0-150 m. Original description is given here under Taxonomic Description.