388 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXIII. 



on the other thorax segments. Sixth segment represented by a median 

 lobe or process attached to the base of the posterior sinus of the geni- 

 tal segment, and without dorsal plates or rudimentary legs. Abdomen 

 short and broad, two-jointed, usually narrowed anteriorly and at- 

 tached to the ventral surface of the genital segment. Abdomen 

 covered dorsally by the rudimentary sixth segment lobe, ventrally 

 by a plate, short and wide, and not reaching the posterior margin of 

 the dorsal lobe. 



Attached to either side of the ventral plate at its base, and to the 

 side of the abdomen, is a peculiarly modified anal lamina; the two 

 are usually divergent, with a thickened conical outer margin and two 

 membranous wings, dorsal and ventral, on the inner margin. Four 



pairs of adhesion pads on the ventral sur- 

 face of the carapace, one pair at the base of 

 the first antennae, one at the base of the 

 second antenna, a third between the bases 

 of the first maxillipeds, and the fourth on 

 the lateral margins of the first pair of thorax 

 plates, opposite the first legs. 



Second maxillipeds much swollen and 

 enlarged, armed with a pair of roughened, 

 forceps-like knobs instead of a terminal claw. 

 Four pairs of biramose swimming legs, the 

 rami all laminate, indistinctly jointed, and 

 usually armed with spines only. Egg tubes 

 straight, uniseriate, close together, and usu- 

 ally much longer than the body. 



Male. — The original type of the genus 

 Nogaus (fig. 16). Carapace broad and well 

 rounded; posterior lobes prominent, triangu- 

 lar, and usually turned inward; posterior 

 margin straight and armed with a pair of 

 secondary lobes, one on either side, close to 

 the base of the posterior lobe; lateral grooves 

 distinct, turned sharph^ outward near the anterior end and extending 

 to the margin of the carapace just behind the first antennte. Frontal 

 plates wide and prominent, anterior margin fairly straight and not 

 deeply cut at the center; eyes often visible in the adults. Free thorax 

 ^segments without dorsal plates, diminishing in width from in front 

 backward, the first one (really the second segment) with a pair of 

 lateral lobes extending diagonall}^ backward and outward, the others 

 without lobes. 



Genital and sixth segments fused, considerably enlarged, and fur- 

 nished with two pairs of rudimentary legs, one, the sixth, at the pos- 

 terior corners, and the other, the fifth, on the lateral margins; both 



Fig. 16.-- Dorsal view of a male 

 or Pandarus cranchii: this 



IS THE "NOGAUS LATREILLII " 



UPON WHICH Leach founded 

 HIS GENUS Nogaus. Drawn 



BY EMERTON. 



