Biology of Pachygrapsus crassipes —HlATT 
137 
Stimpson (1857), Kingsley (1880), de Man 
(1890), Rathbun (1917), and Boone (1927) 
concur in the opinion that Leptograpsus gona- 
grus H. Milne-Edwards, for which the type 
locality is unknown, is identical with P. crassipes 
Randall. The meager description of L. gonagrus 
by Milne-Edwards (1853) agrees with the spe¬ 
cific characters of P. crassipes. Furthermore, 
Milne-Edwards substituted the name Leptograp¬ 
sus for Pachygrapsus. Stimpson (op. cit.) ad¬ 
vanced several reasons for retaining the name 
Pachygrapsus for the group designated Lepto¬ 
grapsus by Milne-Edwards. 
Kingsley (1880), Rathbun (1917), and 
Boone (1927) believe that Grapsus eydouxi 
Milne-Edwards is likewise synonymous with P. 
crassipes Randall. Here again it is obvious that 
the description of G. eydouxi as set forth by 
Milne-Edwards (1853) agrees with that of P. 
crassipes. It seems rather incongruous, however, 
that he should place two apparently similar 
specimens in different genera in the same re¬ 
vision. The type locality for G. eydouxi is cited 
as Chile. If this is correct, G. eydouxi is not 
synonymous with P. crassipes because the latter 
crab does not occur on the Latin American 
coast (see p. 138). 
Systematic Position 
P. crassipes is one of eleven species of a genus 
distributed in a nearly cosmopolitan manner. 
Its members inhabit both the Pacific and 
Atlantic coasts of America, the western coast 
of Africa, coasts bordering the Mediterranean, 
and the Indo-Pacific, and Central Pacific shores. 
Four genera of the family Grapsidae have been 
reported from the California coast; they may be 
readily distinguished from each other (see key 
in Schmitt, 1921: 269). The seven species of 
Pachygrapsus recorded from North and South 
America may be identified by the use of the key 
in Rathbun (1917: 241). 
Description 
Although a moderately complete, generalized, 
morphological description of P. crassipes is 
given by Rathbun (1917: 242), no information 
is made available by this or other authors with 
regard to sexual dimorphism. Measurements 
of the length and width of the carapace of sev¬ 
eral hundred crabs show that the males average 
larger than the females. The mean width of 
the carapace of adult males which ranged in 
size from 16.0 to 45.8 millimeters was found 
to be 36.8, with a standard deviation of 11.2. 
Similar measurements on adult females which 
ranged from 15.0 to 39.7 millimeters showed 
the mean width to be 30.9, with a standard 
deviation of 4.7. The mean length of the cara¬ 
pace of adult males was found to be 31.6 milli¬ 
meters, with a standard deviation of 9.6. Similar 
measurements of females showed the mean 
length to be 26.4 millimeters, with a standard 
deviation of 3.9. These differences in size be¬ 
tween the sexes do not become apparent until 
the crabs reach a carapace width of 22 milli¬ 
meters (see Fig. 10), after which the carapace 
of female crabs becomes relatively narrower and 
shorter than that of male crabs of the same age 
and belonging to the same intermolt period. 
The usual brachyuran sexual dimorphism in 
the abdomen is apparent. Sexual differences in 
the chelipeds are pronounced, those of the male 
being approximately 8 per cent longer. The 
propodite and dactylopodite of this appendage 
exhibit the greatest difference; those of the 
males exceed those of the females by approxi¬ 
mately 10 per cent. 
Type Locality 
The assertion by Randall (1839) that the 
type locality of P. crassipes is the Sandwich 
Islands (Hawaiian Islands), a region outside 
the normal geographic range of this species 
(Fig. 1), has made obligatory an investigation 
of this anomaly. Randall states that the type 
specimen of P. crassipes was collected on the 
shores of the Hawaiian Islands by Nuttall. How¬ 
ever, frequent and thorough searches for decapod 
Crustacea in the Hawaiian Islands during the 
past century, in addition to recent explorations 
by myself, have failed to disclose this species. 
