Xanthosia sakoi n. sp.

Xanthosia sakoi Karasawa, Ohara & Kato, 2008: 107, fig. 2.3. [unavailable].

Type material. HOLOTYPE: WMNH-Ge-1140320064, carapace from Suhara, Yuasa-cho, Wakayama Prefecture (34°2′38.2′′N, 135°11′20.8′′E).

Diagnosis. Moderate-sized Xanthosia . Carapace hexagonal, wider than long, widest at mid-length. Fronto-orbital margin wide. Front bearing 2 rounded lobes, weakly separated from small inner orbital angle. Orbit small. Upper orbital margin narrow with 2 shallow, upper orbital fissures. Anterolateral margin with 4 lobes; first lobe (=outer orbital angle) smallest, acutely triangular; second–fourth lobes broadly triangular; third and fourth lobes larger than second lobe. Posterolateral margin slightly shorter than anterolateral margin, slightly sinuous. Posterior margin slightly concave, narrow. Dorsal surface gently convex, covered with fine granules. Protogastric regions wide, strongly tumid. Mesogastric region flattened posteriorly. Hepatic regions strongly tumid, weakly separated from protogastric regions by shallow, wide depression. Cervical groove sinuous, medially interrupted. Cardiac region pentagonal, flattened. Branchiocardiac grooves shallow. Epibranchial regions slightly swollen. Meso- and metabranchial regions undifferentiated.

Etymology. For Y. Sako who collected the type specimen.