474 KOBERT GTJHNEY. 



abdomen still retains some larval characters. The lateral 

 spines of segments 2 — 5 are still retained, and the telson still 

 shows traces of bifurcation, beiug deeply indented posteriorly. 

 The five pairs of pleopods have the shape characteristic of 

 the typical Brachyurous Megalopa. Those of the first 

 four pairs each consist of a stem bearing a long exopodite 

 armed with numerous long ciliated setae. The endopodite is 

 very small, and interlocks with that of the opposite append- 

 age as a retinaculum. The last (fifth) pair of pleopods have 

 no endopodites, and are shorter than the telson itself. 

 First Post-larval Stage (fig. 14). — Measurement: 



Length of carapace . . . 4*0 mm. 



Breadth (across third lateral spines) . 3"2 „ 



Length of antennas . . . 6"7 „ 



The cast skin of the specimen from which these measure- 

 ments were taken had the following dimensions : 



Length of carapace . . . 3'4 mm. 



Breadth . . . • 2-5 „ 



Length of antennae . . . 4*0 „ 



The Megalopa stage lasts, according to my observations, 

 from eighteen to twenty days, but possibly a more abundant 

 food supply in natural conditions would somewhat shorten 

 the period. 



The young Corystes has now attained the structure of the 

 adult in almost all respects. The rostral spine is reduced to 

 an insignificant tubercle lying at the base of the indentation 

 between the two anterior spines. The dorsal spine is com- 

 pletely lost, though a small orange chromatophore still marks 

 its position on the carapace. The dorsal surface of the cara- 

 pace is smooth, the median ridge of the previous stage and 

 the two anterior dorsal spines having disappeared. 



Besides the three lateral teeth of the Megalopa a fourth 

 tooth is develo})cd behind on each side close to the posterior 

 edge of the carapace, so that the number characteristic of 

 the adult is attained. The cephalo-thoracic appendages show 

 no changes worth noting, except that the endopodite of the 



