THE BRACHYURA AND MAORURA OF PORTO RICO. 
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Genus CHARYBDELLA Rathbun. 
Cronius Stimpson, Ann. Lyc. Nat. Hist. N. Y., vn, 225, 1860. 
Charybdella Rathbun, Proc. Biol. Soc. Washington, xi, 166, 1897. 
Carapace narrow. Front wide; front proper (excluding the inner orbital angle) six-toothed. 
Antero-lateral border cut into nine teeth alternately large and small. Basal article of antenna 
produced into orbital sinus so as to separate flagellum from orbit. 
Key to the Porto Rican species of the genus Charybdella. 
A. Hand armed with four spines rubra 
A'. Hand armed with two spines tumidula 
Charybdella rubra (Lamarck). 
Portunus ruber Lamarck, Hist. Nat. Anim. sans Vert., v, 260, 1818. 
Cronius ruber Stimpson, Ann. Lyc. Nat. Hist. N. Y., vii, 225, 1860. 
Achelous ruber A. Milne Edwards, Arch. Mus. Hist. Nat. Paris, x, 345, pi. xxm, f. 1, 1861. 
Charybdella rubra Rathbun, Proc. U. S. Nat. Mus., xxn, 291, 1900. 
Carapace hexagonal, smooth, and pubescent. Front cut into eight teeth, the two median more 
advanced and larger; directed forward; those of second pair more pointed, directed slightly outward 
and separated from those of third pair by a deep cut; third pair sharp, directed forward, and not deeply 
separated from those of fourth pair, which constitute the inner orbital angles and are broad and blunt. 
Basal article of external antennae carries a spine below insertion of movable portion. Of the antero- 
lateral teeth or spines the ninth is scarcely longer than first, third, fifth, and seventh; intermediate 
spines strikingly smaller. Merus of chelipeds armed in front with from four to six spines of unequal 
size and at extremity of its posterior border with a very small spine. Wrist with granulous crests, a 
large spine inside and three small spines on outer face. Hand crossed by granulous carinse and armed 
above with four spines alternately placed, two on inner border and two on outer border of upper 
surface. 
The general color is a violet red, more or less marbled; extremity of all the spines black (A. 
Milne Edwards) . 
Dimensions of male: Length to sinus, 40 mm. ; extreme length, 42.5 mm. ; extreme width, 68.8 mm. 
Charleston Harbor, S. C., to Brazil; Acapulco; San Salvador, Central America; Panama; West 
Africa from Cape Verde Islands to Loanda. Porto Rico: San Antonio Bridge, San Juan; San Juan 
Harbor, in fish trap; Mayaguez; Arroyo. 
Charybdella tumidula (Stimpson). 
Achelous tumidulus Stimpson, Bull. Mus. Comp. Zool., ii, 149, 1871. 
Neptunus tumidulus A. Milne Edwards, Crust. R5g. Mex., 218, 1879. 
Cronius bispinosus Miers, Challenger Rept., Zool., xvn, 188, pi. xv, f. 2, 1886. 
Carapace narrower than in C. rubra , pubescent, granulated toward margins. Last spine of antero- 
lateral border half again as long as seventh spine. The small alternate spines diminish in the following 
order: Second, fourth, sixth, eighth. Front convex, prominent, projecting much beyond level of outer 
angles of orbits; teeth rounded, the two middle ones being smaller than second pair and most promi- 
nent, separated from second pair by a rather broad, shallow sinus; a narrow sinus between second and 
third pairs. Third pair very slightly separated from inner angle of orbit. The separation of the 
antennal flagellum from the orbit by a process from the basal joint is not so well marked as in C. rubra. 
Chelipeds rather short; merus armed with three large and one small spine on the front edge; spine of 
outer extremity of posterior edge of merus almost obsolete. Inner spine of carpus long, reaching a 
third the length of palm. Only one spine on superior margin of hand; another at articulation of carpus. 
On the merus joint of posterior pair of ambulatory legs is a denticulated extero-inferior margin, but no 
spine. 
Dimensions of male: Length to sinus, 20 mm.; extreme length, 21 mm.; extreme width, 31.2mm. 
Bahamas; Florida Reefs, 37 to 40 fathoms (Stimpson), to Bahia, Brazil, in shallow water (Miers). 
Porto Rico: Mayaguez; Mayaguez Harbor; Boqueron; off Vieques, 14 fathoms, station 6085. Small 
specimens only. 
Stimpson’s description does not agree in all respects with the above, as his type was only a 
quarter of an inch wide. In such small specimens the lateral spine is longer and the notch above the 
antenna is obsolete. 
