(Figure 24 A–I)
Aclis (supranitida var. ?) lata Dall, 1889b: 324–325, plate 18, figure 8.
Aclis lata: Dall (1889a: 126, plate 18, figure 8) [reproduced from original illustration].
Hemiaclis lata: Bartsch (1947: 18, plate 4, figure 4)
Umbilibalcis lata: Bouchet & Warén (1986: 444–445, figure 1056–1057).
Type material. Holotype USNM 126790 (Figure 24A). Type locality. Barbados, 183 m.
Material examined. Type material; USA: USFC stn. 2404 (28°44′N 85°16′W, 110 m), coll. 15/iii/1885: USNM 323963 [1 dd]; USBF stn. 20030 (~24°25′N 82°58′, 164 m): USNM 407033 [1 dd]. Antigua and Barbuda: English Harbor, S.U.I. stn. 496 (219 m): USNM 459689 [1 dd]. Barbados: Off Pelican Islands, S.U.I. Expedition stn. 454 (182 m): USNM 459677 [1 dd]; Off Lazareto, S.U.I. Expedition stn. 497 (171 m): USNM 459708 [1 dd]. Brazil: Rio Grande do Norte: (04°51′S 35°06′W, 375 m), 24/xi/2001: MNRJ 35200 † [1 dd]; Bahia: (11°35′31″S 37°12′18″W, 510 m), 30/x/2000: MNRJ 35268 † [3 dd]; REVIZEE-Central V stn. 504 (14°28′55″S 38°54′03″W, 278 m), coll. Supply Boat Astro Garoupa, 02/vii/2001: IBUFRJ 14399 † [5 dd]; Espírito Santo: REVIZEE-Central V stn. 25a (19°33′28″S 38°45′28″W, 230 m), coll. Supply Boat Astro Garoupa, 28/vi/2001: IBUFRJ 19717 † [3 dd]; Rio de Janeiro: Campos Basin (22°18′53″S 40°11′59″W, 200 m), coll. Supply Boat Astro Garoupa, 18/xii/2004: MNRJ 31867 † [2 dd]; Campos Basin (22°42′33″S 40°41′24″W, 110 m), coll. 19/ix/2003: MNRJ 31881 † [2 dd], MNRJ 31895 † [1 dd]; PADCT stn. 6541: MNRJ 28285 † [3 dd]; PADCT stn. 6627: MNRJ 28287 † [1 dd]; Cabo Frio VII stn. 6194 (24°03′36″S 44°07′36″W, 134 m), coll. RV Almirante Saldanha, 01/iv/1983: IBUFRJ 19727 † [1 dd]; S„o Paulo: REVIZEE Sul stn. 6672: MNRJ 28289 † [1 dd]; PADCT stn. 6573: MNRJ 23226 † [1 dd]; Paraná: REVIZEE Sul stn. 6653: MNRJ 28288 † [1 dd]; Santa Catarina: REVIZEE Sul stn. 6695: MNRJ 28290 † [1 dd]; PADCT stn. 6595: MNRJ 28283 † [7 dd]; PADCT stn. 6606: MNRJ 28286 † [1 dd]; Rio Grande do Sul: off Bojuru (220 m), coll. RV Almirante Saldanha, xi/1979: MORG 21416 † [1 dd].
Redescription (Holotype). Shell conical, straight, reaching about 5.4 mm long, 2.4 mm wide. Larval shell brownish, partially broken. Teleoconch with about 8.0 whorls, slightly convex outline; suture distinct, sloping; subsutural region not visible; surface polished, presenting slightly opisthocline axial lines; incremental scars slightly demarcated, appearing at irregular intervals. Last whorl about 45% of the shell length; base rounded.Aperture wide, pear shaped, acute posteriorly and rounded anteriorly; outer lip thin, slightly prosocline, sinuous, slightly retracted near the suture, reaching a maximum projection in the middle of its height, retracted at distal region; inner lip sinuous, sloping, reflected and well demarcated. Umbilicus present. Shell whitish.
Measurements. Holotype USNM 126790, 10 whorls (protoconch partially broken), SL= 5.4 mm; BWL= 2.5 mm; AL= 1.6 mm; SW= 2.4 mm; AW= 1.2 mm. IBUFRJ 14399, 10 whorls, SL= 5.0 mm; BWL= 2.3 mm; AL= 1.4 mm; SW= 2.2 mm; AW= 1.1 mm.
Remarks. The protoconch is partially broken in the holotype of Umbilibalcis lata (Figure 24A), but the general shape, dimensions and sculpture fits perfectly with specimens from Brazil (Figure 24 B–I). The protoconch of the shells from Brazil have about 3.0 whorls, the first (embryonic) whorl with a smooth surface, the remaining whorls with strongly opisthocline axial lines (Figure 24 H–I). The protoconch is about 270 μm wide and 390 μm in height. A weak brownish band close to suture is present on the protoconch of fresh specimens. The outer lip of the holotype is also partially broken, but it seems uniform in all specimens that the proximal area is slightly advanced, giving a prosocline outline.
Umbilibalcis lata differs from U. crassula Bouchet & Warén, 1986 and U. subumbilicata (Jeffreys, 1883) by the higher number of protoconch whorls (3.0 vs. 1.5 in U. crassula and U. subumbilicata) and by the straighter outer lip (Bouchet & Warén 1986).
Geographical distribution. USA: Florida (present study); Antigua and Barbuda (present study); Barbados (Dall 1889b); Brazil: Rio Grande do Norte, Bahia, Espírito Santo, Rio de Janeiro, S„o Paulo, Paraná, Santa Catarina, Rio Grande do Sul (present study).
Bathymetric distribution. From 60 m to 375 m.