of shorter ramus about as long as fused portion. 

 Antennal scale about three times longer than 

 broad, outer margin concave, terminal spine over- 

 reaching lamella. 



First legs slender ; fingers of chelae longer than 

 palm ; carpus longer than chela. Second legs much 

 stronger than first; smooth; part of carpus ex- 

 tending beyond antennal scale; fingers slightly 

 shorter than palm, but in adult males sometimes 

 only half length of palm, cutting edge of dactyl 

 with two to four, immovable finger with two 

 small teeth in proximal part, adult males with 

 fingers widely agape, opening hairy; carpus short, 

 cup-shaped, half length of merus. Last three legs 

 slender, dactyls bifurcate, propodi with spines 

 present on posterior margin. 



Abdomen smooth, pleura of fourth and fifth 

 segments pointed. Telson with two pairs of dorsal 

 and two pairs of posterior spines; numerous setae 

 between inner posterior spines. Appendix interna 

 present on first pleopods in males, missing in 

 females. 



Measurements. — Length of body : 65 mm. 

 (Holthuis, 1952). 



Variations.- — Dorsal spines on the telson are 

 sometimes not placed in symmetrical pairs and 

 may be asymmetrically doubled. 



Color. — Living individuals : body dark blue 

 green mottled with white: palm of chela uniform 

 blue green, fingers barred; fringes of antennules, 

 antennae, antennal scale and tail fan orange; 

 some individuals colorless, with tawny-tinged 

 spots. Preserved specimens: pale brownish yel- 

 low, tips of fingers brownish red preceded by 

 colorless band, then a fainter band of brownish 

 red; antennular flagella red with white rings at 

 articulations between joints (Holthuis, 1952). 



Habitat. — Found near shore among corals or 

 rocks, and on sea buoys; surface to 4 fathoms. 



Type locality. — Oran and Bone, Algeria. 



Known range. — Virtually pantropical; East 

 and West American coasts, Mediterranean; West 

 Africa; and Indo-Pacific region. Western Atlan- 

 tic distribution: Cape Fear, NX 1 ., through AVest 

 Indies to Curacao and Old Providence. Island; 

 Bermuda. 



Remarks. — Gurney and Lebour (1941) de- 

 scribed a complete series of 11 larval stages and 



a postlarval stage of this species from Bermuda. 

 They pointed out that the larval life of this form 

 may be indefinite in length and number of de- 

 velopmental stages, and that this feature of 

 development may account for the wide distribu- 

 tion of the species. Gurney (1943a) noted pro- 

 portional changes in growth of the segments of 

 the second legs in the last larval stage, first post- 

 larval stage, and adult female. 



Genus Macrobrachium Bate, 1888 



Holthuis, 1952, p. 10. 



Macrobrachium acanthurus (Wiegmann) 



Figures 43-44 



Palaemon acanthrus Wiegmann, 1836, p. 150. 

 Macrobrachium acanthurus: Holthuis, 1952, p. 45, pi. 9, figs. 

 a-b (rev.), 



Recognition characters. — Rostrum almost 

 straight, reaching slightly beyond antennal scale ; 

 upper margin slightly arched basally, with 9-11 

 teeth, proximals closer together than distals, first 2 

 teeth on carapace behind orbit, second tooth some- 

 times partly over posterior margin of orbit and 

 separated from first tooth by distance greater 

 than that between other proximal teeth: lower 

 margin with 4 to 7 (generally 6) teeth, proximals 

 closer together than distals. Carapace smooth, 

 with short hairs especially on anterolateral region ; 

 antennal spine a little below orbit and slightly 

 removed from margin; hepatic spine behind and 

 a little below antennal spine. Antennal scale about 

 three times longer than broad; outer margin 

 straight or convex. 



First legs with chela and sometimes part of 

 carpus reaching beyond scale; fingers as long as 

 palm; carpus one-third longer than merus. Sec- 

 ond legs equal, with carpus and sometimes part 

 of merus reaching beyond scale; fingers slender, 

 thickly pubescent throughout length, slightly 

 shorter than palm, cutting edges with a tooth on 

 each finger in proximal quarter (that of dactyl 

 more advanced) preceded by row of about four 

 denticles; palm elongate, cylindrical, with several 

 longitudinal rows of spinules largest and widest 

 apart on inner and lower regions; carpus and 

 merus spinulose like palm. Articles of last three 

 walking legs with numerous densely placed small 

 spinules. 



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