BRANCHING BRANCHIA 21s 
CHAPTER XVI 
TRIBE VI.—PENEIDEA 
THE branchial structure typically consists of a series of 
plumes, that are attached by, or very near, their basal 
extremity to the animal, and from a long central stalk 
send off on each side a single row of branches that divide 
and subdivide in a variety of ways according to the genus 
or even the species. The appendages of the trunk are 
supplied with nerves from separate ganglionic centres, 
except the last pair, which is supplied not from its own 
segment but the preceding. ‘The third pair of trunk-legs 
are chelate, the two following pairs never are. The ex- 
traded ova do not appear to be definitely attached to the 
appendages of the mother prior to hatching as in most 
other Macrura. The first larval form is supposed to be a 
Nauplius. 
This tribe corresponds with what Spence Bate calls 
the Dendrobranchiata normalia, in allusion to the rami- 
fied, or tree-like structure of the branchizw. He allots to 
it two families, the Penzeidee and Sergestide. 
Family 1.—Penewide. 
The carapace at the sides is deeply produced and 
carried further back than in the median dorsal line; its 
rostrum is laterally compressed, this part at least being 
carinated. Of the segments of the pleon the first three 
are usually not longitudinally carinate, but the three that 
follow are almost always much so. ‘The sides of the first 
are produced so as to overlap the hind lateral margin of 
the carapace and the front lateral margin of the second 
17 
