HORN EXPEDITION—CRUSTACEA. 
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The different species will now be dealt with separately. 
Apus. 
(1) A^us australiensis, Spencer and Hall. (Figs. 1, 2, 3.) 
Reference—Spencer and Hall, Victorian Naturalist, April, 1895. 
Carapace a short oval. Its length about equal to the length of the portion of 
the abdomen which is not covered by the carapace, though this is liable to con¬ 
siderable variation. 
Proportion of greatest breadth of carapace to its median length, 4 : 3. 
Length of carina compared with that of cai-apace, 2 : 3. 
Length from posterior end of carina to posterior angle of carapace, 1 : 2. 
Length of carina compared with median length of carapace, 2 : 3. 
Carina minutely and irregularly serrated and ending in a spine posteriorly. 
Sinus of the carapace with about eighteen minute teeth on each side of the 
mid-line ; sometimes rudimentary or absent in some parts of the margin. 
Posterior outer margin of the carapace with minute serrations which gradually 
become more minute on passing forward until they disappear at about half the 
length of the carapace. 
Dorsal surface of the carapace sparsely covered with irregularly scattered 
minute blunt projections. 
Number of abdominal segments uncovered about twenty-nine. 
Number of abdominal segments not bearing limbs about twelve. 
Each limbless segment of the abdomen with about fifteen sub-equal, short, 
conical spines, arranged in a single row with numerous smaller ones irregularly 
scattered over the under surface. 
The exposed limb-bearing segments with spines on the upper surface and 
sides, becoming obsolete in the anterior segments. 
Telson a little less than twice as long as broad. 
Upper surface of telson with three or four median spines ; a spinous posterior 
border and sides and two or three spines forming a group on each side anteriorly. 
