512 GEOFFREY SMITH. 
bears a pair of delicate leaf-lke gills externally, while 
internally, i.e. towards the mouth, two gnathobasic lobes are 
developed. The limb is flexed between the fifth and sixth 
segments, so that there are three segments distal to the ‘“knee- 
joint’ and five proximal to it. The terminal segment is short, 
and carries, as in all the thoracic limbs of the Anaspidacea, 
three enlarged sete, of which the central one is the largest. 
In Paranaspides the first joint of the endopodite (i. e. 
TExT-FIG. 20. 
Koonunga cursor. First thoracic limb. 
propodite) is expanded towards the mouth to form a definite 
lobe. 
In Koonunga the structure of this limb is aberrant. 
The coxopodite is entirely without gnathobases. ‘here are 
only seven segments in the limb, and since there are three 
segments distal to the “ knee-joint” it is clear that a segment 
has disappeared from below, i.e. proximal to, this joint. 
‘here is no doubt that what has happened is that the propo- 
dite or first joint of the endopodite has fused with the basi- 
