138 
PACIFIC SCIENCE, Vol. II, July, 1948 
Further, Randall states that the type specimen 
of Meto grapsus mess or (Forskal) ( = Pacby- 
grapsus parallelus Randall) was found on the 
coast of Oregon by Nuttall during the same 
voyage. It, in turn, has not been known to 
occur on the American coast, but it is common 
on the Hawaiian Islands. Inasmuch as the names 
are correctly affixed on the type specimens, 
Stimpson (1857) made a rather likely sugges¬ 
tion; namely, that the labels giving the collec¬ 
tion localities of the two species in Nuttall’s 
collection were in some way accidentally ex¬ 
changed. Holmes (1900) also points out that 
several other species reported from the Pacific 
coast by Randall have not since come to light. 
DISTRIBUTION 
Geographical Distribution 
The authenticated geographical range of P. 
crassipes extends along the western coast of 
North America from north latitude 45° (New¬ 
port, Oregon) to north latitude 24°20' (Santa 
Margarita Island, Baja California), and along 
the coast of Japan and Korea from north lati¬ 
tude 34° to 37°. 
A number of records outside the above local¬ 
ities had to be considered in an attempt to 
establish the authentic geographical range. For 
example, Rathbun (1917) cites Chile as a 
collection locality. Correspondence with Dr. 
C. E. Porter, an active carcinologist in Chile, 
has established the fact that P. crassipes does 
not exist along Latin American shores. There¬ 
fore, either Grapsus eydouxi (see Synonymy, 
p. 136) is not synonymous with P. crassipes or 
the type locality of the former is incorrect. 
Rathbun (1902) also cites the Galapagos 
Islands as another locality of collection. The 
specimen upon which the record is based was 
taken at 12 fathoms, a depth in decided con¬ 
trast to the well-known habits of the species 
elsewhere. This, together with evidence sup¬ 
plied by Garth (1946), indicates that P. cras¬ 
sipes is not a member of the Galapagan fauna 
and that the specimen catalogued from there, 
which I have seen and know to be P. crassipes, 
was in some manner mixed with specimens col¬ 
lected from the west coast of America on the 
same expedition. 
P. crassipes is associated geographically with 
but one other congener, P. transversus (Gibbes), 
and with it only toward the southern boundary 
of its range on the east and west coasts of Baja 
California and the west coast of Mexico. Here¬ 
tofore, the two species have been thought to 
overlap in the Galapagos and Cocos Islands. 
A great difference in size enables one to dis¬ 
tinguish quickly between these two forms. The 
length of the carapace of a large specimen of 
P. crassipes is approximately 40 millimeters, the 
width approximately 44 millimeters. P. trans¬ 
versus, on the other hand, is only half as large; 
the length of a large specimen is about 15 milli¬ 
meters, the width about 20 millimeters. The 
most striking diagnostic character is the width 
of the front, which in P. crassipes is half or 
almost half as wide as the carapace; whereas in 
P. transversus the front is distinctly more than 
half as wide as the carapace. 
The geographic distribution of P. crassipes 
is completely disjunctive. The individuals on 
the coast of Japan are separated from those on 
the west coast of America by the wide expanse 
of the Pacific Ocean (Fig. 1). To account for 
this distributional phenomenon, it is necessary 
to assume that the migration between the two 
continents was somehow accomplished without 
leaving tangible evidence of the process. The 
physical characteristics of its habitat (p. 142) 
offer little assistance to the solution of the dis¬ 
tributional pattern, largely because this species 
possesses a wide substrate tolerance and is some¬ 
what eurythermal. Moreover, although rocky 
shore line is common along the coast of Korea 
and Japan, the animals there are restricted to 
a narrow band of latitude 2.5° to 3° in extent. 
The isothermic pattern for surface water and 
air temperature at sea level during both summer 
and winter in Japan and America (see Schott, 
1935) fits a wide latitudinal spread on the 
western coast of North America but is strongly 
