A new genus of leucosiid crabs (Crustacea, Decapoda, Brachyura) from the Red Sea Author Komatsu, Hironori Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7 - 3 - 1 Hongo, Bunkyo-ku, Tokyo 113 - 0033 (Japan) h-komatu @ kahaku. go. jp Author Takeda, Masatsune Department of Zoology, National Science Museum, 3 - 23 - 1 Hyakunincho, Shinjuku-ku, Tokyo 169 - 0073 (Japan) and Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7 - 3 - 1 Hongo, Bunkyo-ku, Tokyo 113 - 0033 (Japan) takeda @ kahaku. go. jp .. takeda@kahaku.go.jp text Zoosystema 2003 25 3 413 423 journal article 10.5281/zenodo.5396755 1638-9387 5396755 Genus Nobiliella n. gen. TYPE SPECIES . — Nursia jousseaumei Nobili, 1905 , by present designation. ETYMOLOGY. — The generic name is dedicated to Dr G. Nobili, who is one of the great carcinologists of Italy . Gender feminine. OTHER SPECIES INCLUDED. — Nursia jousseaumei var. cornigera Nobili, 1905 , which is raised to the specific rank in this paper. DIAGNOSIS. — Carapace subcircular in general outline, convex dorsally, with intestinal and epibranchial ridges; margins and ridges furnished with pearly granules; frontal region moderately produced; orbit with only one fissure on dorsal roof; mesogastric region weakly convex longitudinally; gastro-cardiac region prominently raised, marked with pearly granules on pair of gastric tubercles, with prominent cardiac tubercle; intestinal region prominently raised, with median ridge; hepatic region weakly demarcated, hepatic facet developed; epibranchial margin rounded; epibranchial ridge obliquely running from near gastric tubercle to triangular tooth of metabranchial margin. Basal segment of antennule concealed. Second segment of antenna triangular, subsquamate. Endopod of maxillule reduced. Exopod of first maxilliped reduced. Exopodal flagellum of second maxilliped absent. Internal exopodal ridge of third maxilliped short. Afferent channel with weak oblique ridge; lateral margin with V-shaped notch near anterior end. Cheliped moderate; coxal condyle concealed beneath sternite in both sexes. Ambulatory legs slender; coxal condyles concealed beneath sternites in both sexes. Male abdomen with formula of 1+R+T. Female abdomen with formula of (1)+2+3+R+T; median part of first segment concealed beneath carapace. First male pleopod twisted. Second male pleopod short. Male genital pore with coxal-sternal opening. REMARKS Nobiliella n. gen. contains Nursia jousseaumei and N. jousseaumei var. cornigera , the latter of which is raised to the specific rank in this paper. Nobiliella n. gen. is readily distinguished from Nursia s.s. ( type species: N. hardwickii Leach, 1817 , which is junior synonym of Cancer lar Fabricius, 1798 ) by the absence of mesial fissure on orbital region, the concealed basal segment of antennule, the reduced endopod of maxillule, the reduced exopods of first and second maxillipeds, the fused second segment of male abdomen and the coxal-sternal opening male genital pore. Nobiliella n. gen. is also distinguished from the other species of Nursia by the abdominal formula of male being 1+R+T and the medially concealed first segment of female abdomen. On the other hand, Nobiliella n. gen. is similar to Philyra Leach, 1817 s.s. ( type species: Leucosia globus Fabricius, 1775 ) in the form of carapace, mouth parts and male abdomen and the coxalsternal opening male genital pore, but can be distinguished from Philyra s.s. by the dorsal ridges on the carapace, a lateral triangular tooth on the metabranchial margin, and the medially conceal- ed first segment of female abdomen. Among the species of Philyra , P. malefactrix (Kemp, 1915) and some species close to it are at first glance closely similar to Nobiliella n. gen. in the trilobate posterior margin of carapace, the fused sixth segment of male abdomen and a distal tooth of main fused section of male abdomen. However, Nobiliella n. gen. is distinguished by the distinct dorsal ridges on the carapace, the gastric tubercles covered with pearly granules, the absence of vertical row of setae on the ischium-merus of third maxilliped and the medially concealed first segment of female abdomen. Nobiliella n. gen. is also similar to Praosia Tan & Ng, 1993 , however, it is distinguished by the following features: 1) the carapace has one median longitudinal ridge, whilst that of Praosia has four longitudinal ridges; 2) the second and sixth segments of male abdomen are fused, whilst those of Praosia are divided; and 3) the first segment of female abdomen is medially concealed, whilst that of Praosia is exposed.