RATHBUN— MARINE BRACHYURA 241 



region ; about 7 branchial, separable into 2 groups divided by a groove, 4 tubercles on the 

 posterior area, and 2 or 3 on the anterior. 



Margin of front (between the antennal flagella) a little more than | as wide as the 

 carapace, quadridentate, the median pair of teeth bilobate, the inner lobe the smaller ; 

 median sinus broadly triangular, rounded at the base, other sinuses acute at base. 



Upper margin of orbit cut by 2 V-shaped sinuses separated by a truncate tooth, 

 remainder of margin irregularly crenulate. Outer tooth of orbit falciform, followed by 

 2 acute teeth, the second of which is broad and bidentate and situated at the lateral 

 angle of the carapace. Postero-lateral margins long, convergent, and armed with obtuse 

 teeth or lobes which posteriorly become smaller and more elevated. Posterior margin 

 slightly convex, crenulate, terminating at either end in a small lobe directed laterally. 



The $ abdomen, as in the type species of the genus, M. spinipes (de Man)*, has 7 

 distinct segments, the first very wide and crossed transversely by a sharp and finely 

 granulated crest, fringed above with appressed hairs ; the lateral margin of the second to 

 the seventh segments, inclusive, is sinuous ; surface of abdomen and sternum coarsely 

 punctate. 



The right or larger cheliped of the male is about 1£ times as long as carapace, and 

 bears a heavy propodus ; left cheliped somewhat shorter and much slenderer ; both are 

 pubescent, and have shaggy hair on the upper surface of the fingers ; merus trigonal, 

 dentate on inner margin, granulate above ; carpus tuberculate above, a sharp crest on 

 outer margin. Palm widening distally ; upper surface granulate ; outer edge bimarginate, 

 denticulate; lower surface smooth, punctate; inner edge crenulate, crossed in larger 

 chela by curved stridulating lines, which probably are scraped along the outer surface of 

 the left palm and wrist. Fingers stout, equal in small chela ; immovable about half as 

 long as movable finger in large chela. 



Meropodites of legs broad, margins coarsely serrated ; two rows of spinules above ; 

 carpopodites serrated anteriorly, terminating posteriorly in a small spine ; propodites and 

 dactyli finely dentate, the former nearly covered with superimposed hairs. 



Differs from M. spinipes in carapace wider, surface less hairy, projections less spinous, 

 presence of a distinct stridulating mechanism. 



Grapsidae. 



191. Grapsus longitarsis Dana. 

 Grapsus longitarsis Rathbun, 1907, p. 28. 

 Egmont, reef; 1 large $. 



C. 1. 36-6 mm., C. b. 4T8 mm. Carapace squarish and front broad, as in other, but 

 always smaller, specimens previously examined ; legs relatively shorter and stouter. 



192. Pachygrapsus plicatus (Milne Edwards). 

 Pachygrapsus plicatus Rathbun, 1907, p. 29. 

 Peros, Coin ; 1 $, 1 ?. Coetivy ; 1 $, 1 juv. 



* Conf. Rathbun, 190G, p. 837, pi. 7, tig. 0, text-fig. 3. 



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