32 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



truncated edges finely denticulated, while the posterior, or meso- 

 branchial, is acutely pointed. Inferior lateral regions granulous, 

 and along the lateral borders are clothed with long cilia which pro- 

 ject beyond the margins. There are also some hairs along the lateral 

 margins of the dorsal surface, easily removed. 



Outer surface of external maxillipeds minutely granulous. 



Chelipeds stout, slightly unequal. Merus armed with a spine on 

 the posterior angle, near the distal extremity. Carpus roughened 

 and with a long inner spine. Hands stout, compressed, perfectly 

 smooth: upper edge angular, not crested; fingers compressed, de- 

 flexed, incurved, coarsely and irregularly toothed, not gaping. Legs 

 slender, thickly hairy along the edges, especially on the dactyli, 

 which are long, very slender, and cylindrical. 



Sternum granulous. Abdomen of male smooth, first and third 

 segments much wider than the second, penultimate much broader 

 than long, its sides deeply concave. 



Habits. Probably live in holes, as the crabs have been found cov- 

 ered with ferrugineous mud. (Condensed from Smith.) 



Measurements. Length of carapace of male cotype 15.5, width of 

 same 23.9 mm. 



Range. Panama (Stimpson, Smith). Guayaquil, Ecuador (Cano). 



Genus TETRAPLAX Rathbun. 



Tetraplax RATHBUN, Bull. U. S. Fish Comm., vol. 20. for 1900, pt. 2. 1901, 

 p. 9; type, T. quadridentata (Rathbun). 



Carapace quadrilateral; lateral margins dentate, somewhat con- 

 verging posteriorly. Front about one-third the width of the carapace, 

 margin nearly straight. Orbital margins nearly transverse. Eye- 

 stalks elongate and of moderate thickness. Antennae entering the 

 orbit. Buccal cavity wider in front than behind; maxillipeds not 

 completely filling it, outer angle not produced, inner angle slightly 

 notched. 



Chelipeds unequal, heavy, angular; fingers pointed. Ambulatory 

 legs long, slender, compressed; dactyls of last pair concave upward 

 and outward. 



Abdominal segments in male narrower than the sternum; third 

 to fifth segments fused. 



Contains only one species. 



TETRAPLAX QUADRIDENTATA (Rathbun). 



Plate 6, figs. 3 and 4. 

 Frevillea quadridentata RATHBUN, Bull. Lab. Nat. Hist. State Univ. 



Iowa. vol. 4, 1898, p. 287, pi. 8, fig. 1 (type-locality, Curasao; holotype 



female, Cat. No. 19974, U.S.N.M.) 

 Tetraplax quadridentata RATHBUN, Bull. U. S. Fish Comm., vol. 20, for 



1900, pt. 2, 1901, p. 9. 



