FIJI-NEW ZEALAND EXPEDITION 67 
trunk and then descends. The crab, in turn, crawls backward 
down the tree trunk feeling behind it as it goes. When it feels 
the girdle of leaves it is under the impression that the ground is 
reached and lets go, tumbles heavily to the earth where it is either 
stunned or killed. At any rate, it is then an easy matter for the 
native to catch and tie it up before recovery from the shock of 
the fall. 
Through the kindness of the United States National Museum, 
this University has been presented with two specimens of the 
robber crab, one for inspection and return and the other for pur- 
poses of dissection.® One is a male and measures 15 inches from 
the rostrum to the end of the tail and has a spread of twenty 
inches across the back and over the extended walking legs. The 
total length, including the antenne, is just twenty-four inches. 
The antenne themselves are annulated, like those of the lobster, 
and the antennules have a bifurcated terminal joint. The cara- 
pace, chele and walking legs are very curiously ornamented with 
sharp, transverse, interrupted ridges which are lunate on the 
cephalic region. The chelate appendages are extremely heavy, 
especially the third joint which is greatly thickened and trihedral 
in section. The raised ridges on the hand are broken and there 
are little tufts of hair in front of each ridge. There are six large 
walking legs and a posterior pair which is chelate. The abdomen 
has six well developed terga, the third being much larger than the 
others. Below the terga the abdomen is in the form of a large 
soft-walled sack, hairy on the under surface, and is said to contain 
a supply of oil in the living specimen. Under the distal end of 
the abdomen is the tergum of the last abdominal segment, bearing 
rudimentary appendages and the telson. The female is smaller 
and there are three well developed abdominal appendages on the 
left side bearing long hairs for the attachment of ova. These 
three appendages constitute the only departure from. bilateral 
symmetry and doubtless indicate the descent of this form from 
the hermit crabs. 
The most interesting feature of this strange crab, from my 
point of view, is the respiratory apparatus, especially when com- 
pared with that of the land crabs of the West Indies. In open- 
ing the branchial chamber of Birgus the gills appear, eleven on 
each side in the ventral portion of the chamber and immediately 
above the bases of the hinder pairs of walking legs. These gills 
5 The writer takes pleasure in acknowledging the aid of Mr. Wendell 
Krull, graduate assistant in zoology, in the dissection and study of this. form. 
