THK BRACH YURA AND MACRURA OF PORTO RICO. 
17 
Genus PACHYGRAPSUS Randall. 
Pachygrapsus Randall, Jour. Acad. Nat. Sci. Pliilu., vin, 127, 1839. 
Carapace somewhat narrowed behind and with transverse strife. Sides entire,, or with one or 
two teeth. Front more than half the width of the carapace, moderately deflexed. Inner suborbital 
lobe small, allowing the antennae to enter the orbit. External maxillipeds widely gaping; merus as 
broad as long. 
Key to the Porto Rican species of the genus Pachygrapsus. 
A. Superior margin of palm and movable finger entire transversus 
A'. Superior margin of palm and movable finger denticulate gracilis 
Pachygrapsus transversus Gibbes. 
Grapsus transversus Gibbes, Proc. Amer. Assoc. Adv. Sci., in, 181, 1850. 
Pachygrapsus transversus Gibbes, Proc. Amer. Assoc. Adv. Sci., in, 182, 1850. 
Carapace depressed, shining, with transverse plica?, oblique on the branchial region. Sides 
strongly converging posteriorly, slightly arcuate, with one tooth behind the orbital angle. Frontal lobes 
prominent, front, sinuous. Merus of chelipeds with transverse rugae, inner margin denticulate; carpus 
rugose, with an inner rounded tubercle. Hand minutely granulate, a longitudinal ridge on lower outer 
surface, margins rounded; dactylus with upper margin smooth. Postero-distal angle of the merus of 
the ambulatory legs dentate. 
Dimensions of male: Length, 11.3 mm. ; width at lateral tooth, 14.8 mm. ; width at outer orbital 
angles, 14.5 mm.; width of front below, 8.3 mm. 
Bahamas and Florida Keys to Rio de Janeiro; Bermudas; West Africa; Oriental r.gion; Galapagos 
Islands; California to Peru. Porto Rico: San Juan, on beach; Mayaguez, on re fs; Puerto Real; 
Boqueron Bay; Guanica Bay; Guanica, on reefs; Ponce, on reefs; Arroyo; Cabal lo Blanco Reef, Vieques; 
Ensenada Honda, Culebra; Fajardo. 
Pachygrapsus gracilis (Saussure). 
Melopograpstts gracilis Saussure, M6m. Soc. Phys. Hist. Nat. Gentwe, xiv, 443, pi. it, f. 15, 1858. 
Pachygrapsus gracilis Stimpson, Ann. Lyc. Nat. Hist. N. Y., x, 113, 1871. 
Carapace much as in P. transversus, but with no folds on the cardiac region; lateral margins nearly 
straight, with one tooth. Frontal lobes nearly obsolete; front very broad, nearly horizontal, regularly 
arcuate and minutely crenulate. Hand and dactylus of cheliped spined or toothed above. 
Dimensions of male: Length, 12 mm.; width at lateral tooth, 16 mm.; width at outer orbital 
angles, 15.5 mm.; width of front, 10 mm. 
Bahamas; Florida; West Indies; Yucatan; Sabanilla, United States of Colombia; Rio Parahvba 
do Norte, Brazil; Bermudas. Porto Rico: Boqueron Bay (Fish Hawk ) ; San Juan (G. M. Gray coll.). 
Also taken at Nassau, Bahamas, by the Fish Commission party. 
* Genus ARATUS Milne Edwards. 
Aratus Milne Edwards, Ann. Sci. Nat. (3), XX, 187 (153), 1853. 
Carapace trapezoidal, elongate, narrow behind; sides straight, entire. Front deflexed, very 
broad. External inaxil liped with an oblique piliferous ridge crossing the merus and ischium; merus 
elongate; apex rounded. Ambulatory feet compressed, the dactyli very short. 
Aratus pisonii Milne Edwards. Mangrove Crab. 
Sesarma pisimii Milne Edwards, Hist. Nat. Crust., ir, 76, pi. xix, figs. 4 and 5, 1S37. 
Aratus pisoni MilneEdwards, Ann. Sci. Nat. (3), xx,187 (153), 1853. 
Carapace tranverselv arcuate, branchial regions obliquely plicate. Regions well marked. Front 
vertical, its margin two-lobed. Merus of chelipeds triquetral, margins denticulate, inner margin slightly 
expanded distally. Carpus externally granulate. Hands everywhere granulate, the outer surface of 
palm and fingers ornamented with pencils of stiff black hairs. 
Dimensions of male: Length, 23 mm.; width, 24.5 mm.; width of front, 16.7 mm. 
Florida to Brazil; west coast of Nicaragua; Ecuador. Porto Rico: Mavaguez, in fresh water; 
Boqueron Bay; Puerto Real; Hucares, where it was seen climbing mangrove trees. Also taken at Nassau, 
Bahamas. San Juan, Porto Rico (Gundlach); also collected by G. M. Gray. 
2d— F. C. B, 1900—2 
