THE BRACHYURA AND MACRURA OF PORTO RICO. 
By MARY J. RATHBUN, 
Assistant Curator of Marine Aivertebrates , U. S. National Museum. 
The creatures described in the following paper belong to the well-known class of 
crustaceans, and to that division in which the eyes are mounted on stalks, usually 
movable, and the walking feet are ten in number. 
The terms Brachyura and Macrura are here used in a limited sense, as defined by 
Dana, Stimpson, and Bate. In the Brachyura, or true crabs, the carapace or main 
part of the shell is usually wide and more or less flattened; the front part often 
projects to form a beak or rostrum; the antennae are inconspicuous; the abdomen 
is small, bilaterally symmetrical, and folded under the carapace; of the five pairs of 
thoracic legs, the first pair are furnished with claws and are commonly larger than 
the remaining ones, which are similar. 
The Macrura, or shrimps and lobsters, are elongated — that is, the carapace is 
longer than wide, and either subcylindrical or compressed; the rostrum is usually 
present, and often prominent; the antennae are well developed; the abdomen or tail 
is longer than the carapace and is extensile; any or none of the relatively slender 
thoracic legs may be chelate. 
Crabs and shrimps may be found along the seashore on the sandy and muddy 
bottoms, under stones, in crevices of rocks, corals, and sponges, in shells of living 
bivalve mollusks, in tubes of annelids, and on the tests of sea-urchins. They may 
be taken with the dredge and tangle from all depths of the sea; some species swim 
at the surface, others frequent brackish water at the mouths of rivers. Fluviatile 
crabs and shrimps occur in rivers and streams and along their banks, occasionally in 
ditches or among roots of trees, while the true land crabs may inhabit localities 
remote from salt or fresh water. 
The only systematic list of Porto Rican decapodous crustaceans is that made by 
John Gundlach in his “Apuntes para la Fauna Puerto-Riquena, vi, Crustaceos. ” 1 
Fifty -two species are there enumerated, of which 37 are Brachyura and 8 are Macrura. 
The following list contains 162 Brachyura and 59 Macrura. These species were, with 
few exceptions, taken bjr the naturalists of the Fish Ilawk in 1899. An examination 
has been made, also, of specimens collected by Dr. L. Stejneger, Dr. C. W. Richmond, 
and Mr. Paul Beckwith, of the U. S. National Museum; Mr. A. B. Baker, of the 
'AnalesSoc. Espafi. Hist. Nat., XVI, 115-133, 1887. 
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