426 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



Female. — Carapace semielliptical, widest at its posterior angles; 

 dorsal plates of second segment inclined at an angle of 45° and 

 widely separated, the space between their bases filled with a small 

 central plate; plates of third segment smaller than those of second 

 segment, and nearly in the same transverse line; the plates of the 

 fourth segment circular, meeting on the midline ; plates of second and 

 fourth segments with dentate margins, of third segment smooth. 

 Total length, 3.75-4.25 mm. 



Male. — Carapace narrowed anteriorly, squarely truncated pos- 

 teriorly between the lobes, the latter reaching the posterior margin 

 of the second segment; free segments decreasing regularly in width 

 backward, the fourth segment as wide as the genital segment. Abdo- 

 men half as wide as the genital segment ; caudal rami short and tri- 

 angular, each with four apical setae. Total length, 2.75-3.25 mm. 



Remarks. — This species has been found in a single instance by 

 Brian in the Mediterranean off the coast of Mauretania upon the 

 shark MusteJus asterias. It can be recognized by a large hemi- 

 spherical knob on the ventral surface of the carapace on either side, 

 near the margin and opposite the pad of the maxilliped. The third 

 rami also are as distinctly segmented as the other pairs. 



Genus ECHTHROGALEUS Steenstrup and LUtken, 1861 



Female. — Head fused with first segment, second, third, and fourth 

 segments free, each with a pair of dorsal plates ; those of second seg- 

 ment lateral, of third segment median, both pairs rudimentary and 

 very small ; plates of fourth segment large, covering more than half 

 of the genital segment and extending across the body. Genital seg- 

 ment as large as the carapace or larger, with a deep posterior sinus 

 and long rounded lobes. Abdomen 1-segmented, attached to ventral 

 surface of genital segment, usually partly visible ; caudal rami large 

 and armed with nonplumose setae. First four pairs of legs biramose, 

 rami of first pair 2-segmented; exopods of second and third pairs 

 3-segmented, endopods 2-segmented; rami of fourth legs large 

 lamellae, imperfectly segmented. 



Male. — A Nogaus form, the carapace usually wider than long, with 

 accessory lobes on the posterior margin inside the lateral lobes; sec- 

 ond, third, and fourth segments free, each with a pair of small dor- 

 sal plates, those on the fourth segment scarcely overlapping the an- 

 terior margin of the genital segment. The latter very much smaller 

 than the carapace, more or less quadrilateral with rudiments of fifth 

 legs near the posterior corners. Abdomen entirely visible in dorsal 

 view, and 2-segmented ; caudal rami each nearly as large as the anal 

 segment and armed with four plumose setae. 



