106 
PACIFIC SCIENCE, Vol. VII, January, 1953 
Fig. 36. Crangon brevipes (Stimpson). Variation in 
the frontal region of the carapace, antennules, and an- 
tennae; specimens drawn in a, b, and c came from Wai- 
kiki Beach, Oahu; the specimen in d and e came from 
Mokuleia, Oahu, {a, b, scale A; c, scale B; d, e, scale C.) 
about 5 millimeters long) the propodus bears 
only 4-5 well- developed spines instead of the 
usual 8-11 spines. 
Telson: The measured range of variation of 
the telson has been given. No attempt was 
made to determine whether the small spinules 
on the posterior border of the telson or on the 
posterolateral margin of the inner uropod 
varied in number, as it was too difficult to 
count them accurately. In all specimens that 
were studied carefully the spinules were pres- 
ent. 
These specimens agree perfectly with my 
interpretation of the short description given, 
without figures, by Stimpson; the description 
is adequate to separate this species from all 
other species known to occur in the Hawaiian 
Archipelago. 
Until this species was thoroughly studied, 
it was felt that probably it was identical with 
C. clypeata (CoutiUe), a species found in the 
same habitat; if that had been so, C. clypeata 
would have been relegated to synonymy. The 
two species agree in most characteristics: in 
the general shape and configuration of the 
anterior portion of the carapace; the propor- 
tions of the antennular peduncle and antennal 
peduncle; in the large chela; in the third legs; 
in the telson. 
When a large number of specimens was 
studied, however, the following characteris- 
tics were found to be reliable for their separa- 
tion: 
1. Sexual dimorphism of the small chela of 
males. In C. clypeata the dactylus of the small 
chela of males, although somewhat variable, 
is always noticeably broadened or subspatu- 
late and surrounded by dense setae; in C. hrev- 
ipes it is never subspatulate. 
2. Tooth on hasicerite. This tooth, or spine, 
is almost always present in C. clypeata and is 
always lacking in C. brevipes\ however, in a few 
of the specimens of C. clypeata it is very re- 
duced, and sometimes it is entirely lacking. 
3. Tooth on merus of large cheliped. This 
tooth is usually large and acute in C. clypeata 
and entirely lacking in C brevipes\ however, 
this characteristic alone is not adequate to 
separate the species, as sometimes in C. 
clypeata it may be reduced and obtuse or 
rounded, or even entirely lacking, whereas 
in C. brevipes the margin may bear an obtuse 
projection. 
4. The relative length of the second article of 
carpus of the second legs. In an attempt to find 
the extent of variation in the relative lengths 
of the first and second carpal articles, they 
were measured in 103 specimens of both spe- 
cies; the result of this study is shown in Figure 
37. This shows that most of the specimens of 
C. clypeata have the ratio of the second to the 
first articles of 1.0 and that most of the speci- 
mens of C. brevipes have the ratio of the same 
articles between 1.7 and 2.0, However, speci- 
mens that on the basis of the other character- 
istics were definitely C. clypeata did reach the 
maximal ratio of 1.3, and similarly specimens 
