566 



After the next moult the body ist still longer, but there are no 

 new appendages, although the first four abdominal segments are pre- 

 sent. The fifth and sixth abdominal segments and the telson are re- 

 presented by an unsegmented region, with five pairs of spines. 



The next stage seems to correspond to the Elaphocaris stage of 

 Sergestes, although the spines of the carapace are not compound, the 

 telson is not cleft, and the compound eyes are sessil. The third pair of 

 maxillipeds and the 1., 2., 3, and 4. pairs of pereiopods are present as 

 firamous fuds. The sixth abdominal segment is not yet separated from 

 the telson, and it caiTys a pair of long bilobed buds, the rudiments of 

 the swimmerets. The other five abdominal segments have no appen- 

 dages. 



After the next moult the larva becomes an unmistakable Sergestid, 

 with seven pairs of Mysis-like schizopod feet, which are now the or- 

 gans of locomotion. These seven pairs are the first, second and third 

 maxillipeds. and the first, second, third and fourth pereiopods. The 

 1 . maxilliped has an unjointed exopodite, while the exopodites of the 

 six following appendages are six-jointed, with a pair of long hairs at 

 each joint. The eyes are mounted upon short movable stalks, and the 

 ocellus is still present. 



The first antennae are long, three-jointed, with six plumose hairs 

 upon the inner edge. The second antennae have undergone very great 

 change. They are less than half as long as the first pair: the outer 

 ramus is about as long as the inner; both are unjointed and without 

 hairs. 



The telson is separate from the sixth abdominal segment ; and the 

 swimmerets are longer than the telson, fringed with plumose hairs, 

 and functionally perfect. The other abdominal appendages are not 

 present. The carapace is shaped like that of Sergestes ; there is a long 

 rostrum, and a pair of antero-lateral spines, but no posterior spines. 



At the next stage the exopodite of the second antenna has become 

 a scale, fringed with plumose hairs, and the endopodite is jointed, 

 hairy, and about as long as the first antenna. The abdominal feet are 

 now present as buds. 



After the next moult the antennae are a little longer ; the outer 

 ramus has disappeared from the second and third maxillipeds and from 

 the pereiopods, and these appendages have their adult form. A trans- 

 verse fold near the anterior edge of the carapace marks the line where 

 the elongation to form the neck will take place. 



The second, third, fourth and fifth abdominal feet next become 

 biramous, and hairy, the neck elongates; and when the larva is about 

 one fourth of an inch long it is substantially like the adult, the only 



