FRONTAL APPENDAGE—PHYLLOPOD CRUSTACEAN haul 
In tracing the various parts of the large trunk to their endings 
in the tips of the branches, cross, as well as longitudinal, sections 
were used. At the forking of the large trunk, the right and left 
halves which compose it separate, one part going to each branch. 
In these branches as well as the various sub-branches the different 
tissues occupy the same relative positions as they do in either 
half of the trunk. All the tissues extend into the very tips of 
the appendages and in all the branches the flexor muscle occupies 
an area proportional to that taken by it in the half of the main 
trunk from which it is derived, the muscle tapering gradually 
from the main trunk to the tips of the various branches. The 
parts of the diminishing muscle find attachment on the lateral 
and ventral walls of the particular branch which they occupy. 
Posteriorly, the large flexor muscle increases in size, reaching 
its greatest thickness just after its entry into the head. At this 
point it bends slightly ventro-laterally and is met by the large 
muscle of the second antenna. From this point these two muscles 
bend still farther in the same direction, and at the same time 
flare out into a fan-shaped bundle, extending to their point of 
origin on an inbending of the chitinous covering just in front of 
the large mandibles (fig. 3). In passing through the head to 
their point of attachment these two muscles are in such close 
proximity that they appear almost as a single large muscle. 
Fig. 4 Optical section of tip of branch of frontal appendage of Thamnocephalus 
Platyurus. 
The antennal muscle does not lie beside and in the same plane 
with the retractor muscle of the frontal appendage, but in a more 
ventro-lateral position along its mesial surface. The muscles 
in the distal end of the appendage extend out into the small, 
claw-like structures as small bundles. Whether these claw-like 
tips (fig. 4) are used in clasping or as tactile organs is unknown. 
