Gaza rathbuni Dall, 1890

Simone, Luiz Ricardo L. & Cunha, Carlo M., 2006, Revision of genera Gaza and Callogaza (Vetigastropoda, Trochidae), with description of a new Brazilian species, Zootaxa 1318 (1), pp. 1-40 : 19-20

Gaza rathbuni Dall, 1890

( Figs. 33–40 )

Gaza rathbuni Dall, 1890: 394 . 1890: 342 (pl. 7, fig. 4). Abbott & Dance 1983: 40 (unnumbered text­fig. of holotype). Keen 1971: 342. Finet 1995: 23.

Types: Holotype USNM 97054 (examined).

Type locality: Ventana Bay , near Galapagos Islands , 24°11’30”N 109°55’00”W, 717 m depth ( R / V Albatross, Sta. 2828, United States Fish Commission, 30/iv/1888) .

Diagnosis: Color of entire shell pale­beige iridescent, smooth, spire low with about five whorls. Protoconch without hole in adult. Body whorl with very low spiral lines. Height/width 1.40 on average. Weak carina at middle level of body whorl. Umbilicus completely covered by callus. Epipodial tentacles: 7 on right side.

Distinctive description

Shell ( Figs. 33–40 ): Size about 35 mm. Color beige with green tinge. Outline discoid ( Figs. 33 , 37 ); spire low, height 10% more than half of body whorl, about half its volume. Spire profile forming flat dome; whorls weakly convex, suture almost plane, weakly marked. Protoconch smooth, dome­shaped, of two whorls ( Figs. 34 , 38 ). Sculpture of only weak spiral, about 25 spiral lines in penultimate whorl. Teleoconch up to 4.5 whorls. Peristome, umbilical regions similar to those of G. compta , including umbilical chamber completely sealed by callus ( Figs. 35, 36 ).

Measurement of shells (in mm): Holotype = 38.0 x 27.0; AMNH 254993: 32.5 x 22.0.

Distribution. From Galapagos Island to western coast of Panama.

Habitat: In sand, from 200 to 717 m depth.

Material examined: Holotype: USNM 97054 . PANAMA, off Cape Mala (Pacific Ocean), 200 m depth, AMNH 254993 , 1 shell (Helen DuShane collection, sta. KN 113, ix/ 1975).

Remarks: Although the specimen AMNH 254993 ( Figs. 33–36 ) was not found close to Galapagos, the collection locality is sufficiently close, and the shell attributes are very similar to the G. rathbuni holotype ( Figs. 37–40 ), which confirm its identification. This AMNH specimen is important in having the peristome and umbilical flap completely developed. It provides the basis for a complete description of all shell characters, which is not possible from the immature holotype ( Figs. 37, 39, 40 ). However, AMNH specimen is not a topotype; additionally, the immature holotype is larger than the fully grown AMNH specimen.

Some anatomical data of this species were given by Dall (1890), who reported the presence of seven epipodial tentacles on the right side.

Figures

FIGURES 24–36. Gaza spp. Figs. 24–27: G. olivacea FMNH 223560 (from Surinam). Figs. 24–26: Shell, apertural, apical and umbilical views. Fig. 27: Detail of umbilical area. Scale bar = 10 mm. Figs. 28–32: G. fischeri Paralectotype USNM 94989. Figs. 28–30: Shell in apertural, apical and umbilical views. Fig. 31: Detail of umbilical area. 32. Operculum, outer view. Scale bar = 5 mm. 33–36. G. rathbuni AMNH 254993 (off Cape Mala, Panama) shell. Figs. 33–35: Apertural, apical and umbilical views. Fig. 36: Detail of umbilical region. Diameter = 32.5 mm.

FIGURES 37–48. Shells. Figs. 37–40: Gaza rathbuni Holotype USNM 97054. Figs. 37–39: Shell in apertural, apical and umbilical views. Fig. 40: Detail of umbilical area; Diameter: 38 mm. Figs. 41–44: Callogaza watsoni Holotype MCZ 7544, a specimen with peristome not formed. Figs. 41–43: Shell in apertural, apical and umbilical views. Fig. 44: Detail of umbilical area; Diameter = 11 mm. Figs. 45–48: C. sericata MZSP 48530 from Aliguay, Philippines. Figs. 45–47: Shell in apertural, apical and umbilical views. Fig. 48: Detail of umbilical area. Diameter = 15 mm.