28o DISCOVERY REPORTS 



spicuous dorsal organ. Its median posterior projection has a wide base and it reaches 

 well beyond the hinder margins of the postero-lateral wings. 



The antennular spine is as long as in the third Calyptopis ; the flagella are unseg- 

 mented. 



The degree of development of the thoracic limbs is as follows : 



Second limb. Long and bifurcate, the endopod with terminal setae ; a strong gill bud. 



Third limb. Usually short, about half as long as second, showing beginnings of bud- 

 ding off of exopod and gill at once ; less often, longer and bifurcate, non-setose, with a 

 small gill bud. 



Fourth limb. Always free. Usually simple and less than half as long as third, some- 

 times beginning to show that exopod and gill will be budded off together. 



Fifth limb. Not free. 



There is a pair of very small lateral protuberances from the tergum of the first ab- 

 dominal somite, the beginnings of the tergal wings of the adult (Fig. 38 c). There may 

 be no posterior dorsal spines on the third to fifth abdominal somites, or very small 

 spines on the fourth and fifth, or on all three. 



The telson is similar to that of the third Calyptopis. 



Fiircilia, stage II 



Description based on the examination of ten specimens. One hundred and twenty-nine were 

 measured and were 5-0-6-5 mm. long. 



In this stage there are four pairs of setose and one pair of non-setose pleopods. 



The frontal plate is a little reduced in width and length compared with the previous 

 stage, the rostral spine is stronger : this is a process which is continued in each of the 

 larval stages which follow. The rostral spine reaches nearly as far forward as the end of 

 the basal segment of the antennular peduncle. The dorsal organ is very strong. The 

 median posterior projection of the carapace has gone, leaving only a low rounding of the 

 margin in its place. 



The antennular spine is still longer than the sum of the second and third peduncular 

 segments. The flagella are usually unsegmented, sometimes beginning to segment. 



The degree of development of the thoracic limbs is as follows : 



First limb. Endopod still of two segments as in earlier stages, usually only a little 

 longer than exopod. No gill bud. 



Second limb. Endopod of five segments and feebly kneed. A two-branched gill bud. 



Third limb. Endopod with five or less segments indicated, or of five segments. Gill 

 bud beginning to branch or of two branches. 



Fourth limb. Short, bifurcate, endopod non-setose or setose. Gill bud unbranched 

 or branching. 



Fifth limb. Very short, non-setose, usually bifurcating and budding off a gill, or with 

 a small gill bud. 



