NEW SPECIES OF CALTGUS. 59 



are adapted for swimming ; and the sixth and last pair are long 

 (longer and more powerful in the male than in the female), and 

 in both they are furnished with claws, five in number. 



The swimming-apparatus is exceedingly elaborate in its 

 structure, and consists of two sets of plumose setae, eleven in 

 number, placed at each side of the head behind the lunules, and 

 in front of two long antennae, which project at almost right angles 

 from the median line. The fifth pair of legs already mentioned 

 form also part of the swimming-mechanism. These legs have 

 each a strong tarsus, and upon this are articulated two joints, 

 short, and nearly at right angles to each other ; one furnished with 

 eight long plumose setae, the other provided similarly with seven. 

 Ranged immediately behind, quite on the posterior edge of the 

 carapace and projecting backwards, there are, on each side, two 

 pairs of semi-circular flap-like swimming-plates, also plumose 

 and capable of motion. 



The female has a larger abdomen than the male, and in it are 

 to be detected convolutions of what appear very much like eggs 

 in the ovaries. There is a double tail, having at each extremity 

 three long plumose setae, not unhke the double tail of Cyclops 

 quadric07-nis. 



'Jlie eye. Fig. 5, is placed on the upper side of the cephalo- 

 thorax, in the median line, and just opposite to the mouth, which 

 is, as already stated, on the under side. On careful examination 

 with the quarter-inch, the eye is found to be double, composed of 

 two lenses placed back to back, separated by a comparatively 

 v/ide septum, and thus capable of looking in opposite directions. 



It is not unlikely that, as is the case with Cyclops and some of 

 the Entomostraca, the respiration is anal ; and when the living 

 animal is viewed in a favourable light, a movement corresponding 

 to such respiration may be detected. 



The female bears two ovisacs at each side of the tail, in 

 which the eggs may be seen closely packed together : they are 

 long, narrow, and transparent; very easily detached, and about 

 as long as the creature itself 



The cephalothorax is fringed all round with a very finely 

 striated, gelatinous fin, of such exceeding tenuity that it almost 

 disappears from view when traced along from the front, where it is 



