Xestoleberis toni ? ANTONIETTO et al., 2012:40-41, Figs 6:9-12; Tab. 8 (non Xestoleberis toni WOUTERS, 2003:152, Pl. 9, Figs 1 -8; Pl. 13, Figs 5a-c).

Xestoleberis sp. 1 COIMBRA et. al., 2013:297, Figs 58-61; Tab. 4.

Type material. Holotype, MP-O-2474, ♀, RV, length: 0.42 mm; height: 0.22 mm. Paratypes. MP-O-2475, ♀, LV, length: 0.41 mm; height: 0.22 mm; MP-O-2476, ♀, carapace, width: 0.19 mm; length: 0.40 mm. MP-O-2477, ♂, RV, length: 0.44 mm; height: 0.21mm.

Etymology. From Brasil and the Latin origin, insularis = of an island, because of its record being restricted to an archipelago.

Type locality. Archipelago of São Pedro and São Paulo, Equatorial Atlantic.

Occurrence. See Table II.

Diagnosis. Small-sized and relatively thin carapace. Subovate elongate to subrectangular in lateral view; ovateelongate in dorsal view. Greatest length just below midheight. Greatest height just posterior mid-length. Anterior margin obliquely rounded, with apex in the lower third. Posterior margin subtruncated. Surface typically smooth with two types of normal pore canals: sieve-type and liptype. A very delicate flange, more developed in RV, runs along the anterior and ventral margins.

Description. A relatively thin-shelled and small-sized species of Xestoleberis. Subovate elongate to subrectangular in lateral view. In dorsal view, ovate-elongate. In ventral view, flattened. LV overlapping RV mainly anteriorly and posteroventrally. Maximum length just below mid-height. Maximum height just posterior mid-length. Maximum width posteriorly.Anterior margin obliquely rounded, with apex in the lower third. Posterior margin subtruncated. Dorsal margin moderately arched. Ventral margin sinuous near the middle, more conspicuously in RV. Surface typically smooth with two types of normal pore canals (sensu SATO & KAMIYA, 2007): sieve-type and lip-type. A very delicate flange, more developed in RV, runs along the anterior and ventral margins. In living specimens, some very short marginal bristles overlaps the flange forming a false delicate reticulum when photographed by SEM (see Figs 3, 9). Xestoleberis -spot small and almost invisible; around it there is a milky patch. Inner lamella wide at anterior, narrow ventrally and posteriorly. Line of concrescence and inner lamella widely separated anteriorly, forming a large vestibulum. Posterior vestibulum very small, visible only in large magnification. Selvage subperipheral in both valves, bending outwards in the oral region. Marginal pore canals numerous and short, mostly simple and straight, as typical for the genus. Hinge hemimerodont, with welldeveloped crenulate terminal teeth in RV; median element smooth. Central muscle scars constituted by four adductors vertically aligned and a frontal U-shaped. Two mandibular scars below in front. Sexual dimorphism: females more inflated posteriorly, somewhat more height and with a more marked oral concavity. Males more rounded posteriorly.

Remarks. Xestoleberis brasilinsularis sp. nov. was identified by ANTONIETTO et al. (2012) as Xestoleberis toni ? Wouters, 2003. However, as already briefly discussed by COIMBRA et al. (2013), these two taxa are not conspecific. In fact, they have not only different outlines, but also different central muscle scars pattern and Xestoleberis spot, that is larger in the species described by WOUTERS (2003) for Cape Verde Islands. The new species does not fit well in any Xestoleberis morphological group proposed by BONADUCE & DANIELOPOL (1988) neither by SATO & KAMIYA (2007).