274 DISCOVERY REPORTS 



The buds of the second to fifth thoracic Umbs are free. The degree of their develop- 

 ment varies from (i) second bifurcate and nearly as long as first, endopod with terminal 

 setae, gill bud present ; third bifurcate and less than half length of second, with no setae, 

 gill bud present; fourth not bifurcate, very short with no gill bud; fifth a very small 

 simple bud ; to (ii) endopod of second of five segments and nearly as long as first ; third 

 more than half length of second, endopod with terminal setae; fourth much shorter 

 than third but bifurcate and beginning to bud off a gill ; fifth showing the beginnings of 

 bifurcation and the budding of a gill. 



The tergal wings of the first abdominal somite are well developed and connected 

 dorsally by an upstanding collar-like ridge. This tergal "collar" is very easily seen and 

 it is the best character for distinguishing between this stage of E. vallentini and E. 

 frigida (Fig. 37 e and/). 



Fur cilia, stage III 



Description based on the examination of thirty specimens. Of ninety-eight specimens measured 

 two were 5-0 mm., one was 5-2 mm. and the remainder 5-4-6-I mm. long. 



In this stage there are five pairs of setose pleopods and the antennal endopod is un- 

 segmented. 



The carapace has a prominent and unmistakable dorsal organ. The frontal plate is 

 most frequently triangular with strongly or moderately convex sides; it is sometimes 

 rounded with a central spine, more rarely rounded with no central spine. 



The antennular spine reaches about halfway along the third peduncular segment. The 

 flagella are either unsegmented or beginning to segment and about equal in length to the 

 sum of the second and third peduncular segments. The mandibular palp is unsegmented. 



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



First limb. Endopod of two segments as in earlier stages, no gill bud. 



Second limb. Longer than first, endopod of five segments and feebly or strongly 

 kneed. 



Third limb. Endopod of five segments, usually not kneed and as long as to knee of 

 second, sometimes longer and kneed. 



Fourth Umb. Endopod not segmented, or beginning to segment, terminal and other 

 setae, one-third to more than half as long as third, a strong gill bud. 



Fifth limb. Bifurcate, without or with setae, one-third to more than half as long as 

 fourth, a gill bud. 



Sixth hmb. A low bud rarely bifurcate but usually with a small gill bud. 



Seventh limb. A gill bud usually, but not always, developed. 



Eighth limb. Usually not developed, rarely a small gill bud. 



The tergal wings of the first abdominal somite are joined dorsally by a collar as in the 

 previous stage. 



There may be seven, six or five terminal spines on the telson. Of the specimens ex- 

 amined forty-seven had seven terminal spines, seven had six and fifty-seven had five 

 (see Table I, p. 256 and pp. 257-8). 



