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145 
burrows) and were almost twice that size 
(carapace length of 13»5 mm., total length to 
32 mm.). Because of this difference in size and 
habitat the individuals were carefully studied 
to see if any specific differences occurred be- 
tween them. The large specimens were found 
to fall well within the range of variation of 
the small specimens. The difference in size 
may be due to the difference in habitat. The 
difference in the depth of burrows may be due 
to the underlying substrate of coral in the 
mud flats which prevents them from excavat- 
ing their burrows as deeply as they can in the 
pure sand of the bar. 
The variation in a group of 30 specimens, 
including the 2 large specimens, was tabu- 
lated with the following results. 
Antennular peduncle: Second article from 
1.4 to 2.5 times the length of the first. Third 
article from 0.6 to 1.1 times the length of the 
first. 
Scaphocerite: Usually slightly to definitely 
longer than both carpocerite and antennular 
peduncle. 
Carpocerite: Usually equal or subequal in 
length to the antennular peduncle; in two 
specimens, otherwise normal, equal in length 
to the scaphocerite, definitely longer than 
antennular peduncle. 
Large chela: Total length usually 1.5 to 1.8 
times breadth. Fingers usually 0.4 to 0.7 
length of palm. 
Small chela: Palm 1.2 to 1.5 usually 1.4, 
times as long as broad in males, 1.1 to 1.8, 
usually 1.3, times as long as broad in females.^ 
Fingers 1.5 to 1.8, usually 1.7-1. 8, times the 
length of palm in males, 1.4 to 1.8, usually 
1.4-1. 6, times length of palm in females. 
Carpus, second legs: Second article 0.7 to 
1.0 times length of first article, with most 
0.8 times. 
In one specimen a very peculiar large and 
small chela was noted. In this specimen the 
^ In my original description of the Hawaiian speci- 
mens (1953: 128, top line, left column) there is an 
error for the palm was 1.5, not 2.5, times as long as 
broad. 
Fig. 9. Alpheus rapax Fabricius. Aberrant large and 
small chelae, a, b. Normal large and small chelae of 
male; c, d, aberrant large and small chelae, male. All 
drawn to same scale. 
fingers of the large chela were 1.1 times the 
length of the palm, and the small chela was 
much thinner than usual, and not halaenicepS’ 
shaped as would be expected for a male. 
(Fig. ^c-d contrasts these chelae with normal 
male chelae of approximately the same size.) 
All other characteristics are like those of the 
typical A. rapax. A similar condition has been 
previously reported. De Flaan (1850: 178, 
pi. 45, fig. 4) described a new species, A. 
digitalis, separated from A. rapax only by the 
great elongation of the dactylus of the large 
chela. Coutiere (1898^:248) examined the type 
of this species and two other species of the 
genus described on the basis of similar char- 
acteristics, and came to the conclusion that 
these were examples of regeneration where 
the development was arrested "a un stade 
