[mcmuURRICH] PLANKTON OF BRITISH COLUMBIA COAST 85 
The last thoracic segment is narrow but quite distinct from the 
preceding one; its lateral lobes symmetrical and terminating in an 
acute angle, but not prolonged into well-marked expansions (fig. 8). 
The outer rami of the 1st-4th thoracic limbs are 3-jointed, the inner 
ramus of the 1st limb is 3-jointed (fig. 10), but those of the 2nd-4th 
limb are 2-jointed. The 5th limb (fig. 11) is symmetrical on the two 
sides, the proximal basal joints are united in the medial line and the 
Fie II 

Fig. 10. First thoracic limb of Paralabidocera amphitrites © 
Fig. 11. Fifth thoracic limb of Paralabidocera amphitrites Q 
distal basal bears upon its posterior surface a single feathered seta 
attached about half way between the proximal and distal borders and 
extending only a short distance beyond the latter. The outer ramus is 
single-jointed and is almost straight; it terminates in a pointed pro- 
jection, a smaller tooth occurring at the inner side of its base, while 
two small teeth are borne upon the outer border. The inner ramus is 
also single-jointed and articulates with the distal basal joint; it is 
also almost straight, is bellied out on its inner border proximally, 
terminates into two short teeth and is a little less than one-third the 
length of the outer ramus. 
Male.—The head region of the male resembles that of the female 
except that the lenses of the dorsal eyes are considerably larger.» 
The left first antenna is very similar to that of the female, but the 
right one (fig. 12) is considerably modified. The basal joints are 
broader and there is no fusion of joints, except a partial fusion of 1st 
and 2nd, so that all the twenty-five joints of which the limb is composed 
can be readily distinguished. The 3rd-8th joints are narrow, and each 
bears three aesthetasks (all of which are not shown in the figure): a 
