TYPE SPECIES. — Arctus bicuspidatus De Man, 1905 by present designation.

OTHER SPECIES. — So far two species are assigned to this new genus: Crenarctus crenatus (Whitelegge, 1900) n. comb. and the type species C. bicuspidatus (De Man, 1905) n. comb. As Arctus crenatus is based on a juvenile specimen, A. bicuspidatus is chosen here to be the type species of the genus Crenarctus n. gen.

ETYMOLOGY. — From the Latin crena (= notch) and the generic name Arctus De Haan, 1849, in reference to Arctus crenatus Whitelegge, 1900, the first species of the genus to become known.

DIAGNOSIS. — The rostral tooth is distinct and so is the pregastric tooth. The gastric tooth is represented by two tubercles on the posterior margin of the pregastric tooth. The cardiac tooth is low and two-topped; it is distinctly lower than the pregastric tooth. The anterior tooth of the posterior submedian ridge is almost as strong as the cardiac tooth and lies in about one transverse line with it. The abdominal somites show the typical arborescent grooves and have no median carina.

The upper surface of the fourth antennal segment bears a single strong oblique carina, there are no additional carinae or rows of tubercles. P.1 is much more robust than P.2. The dactylus of P.2 is longer than the other dactyli. None of the dactyli shows a hairy fringe. The propodus of P.3 but not of the other legs has a dorsal fringe of hairs. The carpus of P.3 and P.4 have a dorsal fringe of hairs. Such a fringe is also seen on the merus of P.2 to P.5.

The anterior margin of the sternum is shallowly U-shapedly concave and shows a tubercle at either side of the median incision.

KEY TO THE SPECIES OF CRENARCTUS N. GEN.

Species dealt with in this paper are in bold.

— Anterior submedian carina ending in a strong anterior tooth. Median area of second abdominal somite elevated anteriorly and ending in a blunt lobe............................................................................................................................ C. crenatus n. comb.

— Anterior submedian carina with a few inconspicuous flat tubercles, none of which ends in an elevated tooth. Median area of second abdominal somite not elevated but flush with the rest of the surface, no anterior median elevation........................................................................................................................ C. bicuspidatus n. comb.