652 CRUSTACEA. 



tennse very stout at apex of base, the last joint of base being hardly 

 oblong. Thoracic feet very slender, short and sparsely ciliate, claw 

 oblong and very slender, palpus much shorter than pediform branch. 

 Last abdominal segment longitudinally deeply concave above, nearly 

 half shorter than outer caudal lamella, broadest at base, short fur- 

 cate at apex and acute, sides short spinulous. Outer caudal lamella 

 much longer than inner, ciliate on both margins. 



Plate 43, fig. 4 a, animal, enlarged ; b, caudal lamellae, enlarged, 

 the caudal segment removed ; c, caudal segment, enlarged to corre- 

 spond; c', same, in oblique side view. 



China Sea, four hundred and fifty miles from Singapore, to the 

 northeast. Collected, February 16, 1842. 



Length, two-fifths of an inch. A little reddish yellow along the 

 venter. The carapax has a slight depression dorsally, not far* from 

 the front, as if indicating the separation of a cephalic portion; and 

 another just back of beak. The beak is acute. The last abdominal 

 segment is longitudinally deep concave, and ends in two acute points 

 separated by a rounded emargination. The segment narrows from its 

 base with a curve, the narrowing scarcely perceptible near apex. The 

 last joint of base of first antennae is very stout, nearly as broad as 

 long. Penult joint of base of outer antennae three times as long as 

 last joint of base. Flagella of antennae were mutilated ; but enough 

 remained to show that they were quite long and very slender. The 

 upper of first pair is stouter and hairy at base. 



The abdominal appendages all well developed, being of full length, 

 and consisting of a base and two oblong ciliate lamellae. The seta?' 

 were short. 



Genus MACKOMYSIS, White. 



Carapax plus mimisve rostratus. Antenna internee flageUU duobus ' 

 lamindque oblongd confectce. Ocull symmetric!, breduscidi Pedes 

 thoracis sexdecim, toti palpo natatorio midtiarticulato instructi tarso 

 simphce, unguiculato. Pedes abdominis plerumque parmdi guurti 

 valde elongati. tegmentum abdominis posticum bilobatum vel emar- 

 gmatum.J 



