THE BRACHYURA AND MAORURA OF PORTO RICO. 
105 
Genus ALPHEUS Fabrieius. Coutiere. 
Alpheus Fabrieius, Suppl. Entom. Syst., 380, 1798; Ooutiere, Ann. Sci. Nat. (8), Zool., lx, 336, 1899. 
Carapace smooth. Rostrum of variable shape. Orbital arches usually very complete, isolated 
by an orbito-rostral depression and an orbito-antennal sulcus; formed by excessive development of 
extra-corneal spines, of which the point frequently remains. No pterygostomian spine. Antennules 
with basal article and spine reduced. Distal article of third maxillipeds drawn out to a point and 
almost unarmed. Thoracic feet with epipods. First pair with an asymmetry usually very marked. 
Carpus very short, hemispherical. Chelte depressed, of variable form. Third to fifth pairs of feet with 
propod i strongly spinulous; dactyli usually simple, sometimes lanceolate. 
Key to the Porto Rican species of the genus Alphem. 
A. Carapace without median spine at base of rostrum. No long spine between rostrum and eyes. 
B. Orbit with a small spine on the margin. 
C. Propodus of large eheliped notched on both margins. 
D. Basal antennal spine very short, not reaching second segment of antennula. Antennal scale no longer 
than antennular peduncle macrochetes 
O'. Basal antennal spine reaching second segment of antennula. Antennal scale longer than antennular 
peduncle ilentipes 
C'. Propodus of large eheliped not notched on margins .formoms 
B'. Orbit without a spine. 
C. No basal antennal spine eristnlifrons 
C'. A basal antennal spine. 
D. Orbital margin forming a projecting tooth. Both surfaces of large hand with a longitudinal groove, 
between these grooves a tooth packard ii 
I)'. Orbital margin simply rounded, without a tooth. 
E. Hands of large eheliped notched on both margins heterochxt is 
E'. Hands not notched on the margins. 
E. Hand with two longitudinal grooves on outer surface rostratipes 
F'. Hand with one groove on either surface leading from pollex Jloridanus 
A'. Carapace with a. median spine a I base of rostrum. A long spine between rostrum and eyes armalus 
Alpheus macrocheles (Hailstone). 
Hippolyte macrocheles Hailstone, Mag. Nat. Hist., vm, pp.-. 395, 519, 552, 553, 1835. 
Alpheus megaehelea Norman, Ann. Mag. Nat. Hist. (4), ir, 175, 1868. 
Rostrum a short, acute spine, much shorter than first antennular segment. Orbital margin with 
a smaller spine, less advanced than rostrum. Third antennular segment half as long as second. 
Basal scale broad, triangular, tipped with a spine reaching nearly to second segment. Antennal 
peduncle longer than antennular. Scale equal or nearly equal to antennular peduncle. Basal spine 
very short, shorter than antennular scale. Propodus of large eheliped much compressed, with upper 
and lower margins notched. Distal portion of outer face with three longitudinal furrows; the crest 
between middle and lower furrows prolonged into a spine between bases of fingers. Superior margin 
of dactyl us with a Jhiir, sharp edge. Smaller eheliped also broad; propodus with both margins 
notched, upper notch very feeble; outer face marked with shallow grooves, and a spine at base of 
fingers, similar to those in the large eheliped, but less strong. The carpal joints of the second pair 
diminish as follows: First, second, fifth, fourth, third; the first or proximal joint being the longest. 
Length of European specimen, 24.8 mm. 
A large chela of a small specimen of this east Atlantic species was taken in Mayaguez Harbor, 
lfil to 172 fathoms, station 6066. In this claw the distal extremity of the upper margin is spiniform 
instead of lobiform as in the large European specimens that 1 have at hand; the superior furrow of the 
outer face is longer, extending two-thirds the length of the palm. The marginal notches are slight. 
It is possible that this claw belongs to a distinct species. 
A. macrocheles is known from Europe and West Africa. 
Alpheus dentipes Guerin. 
Alpheus dentipes Guerin, Exp. Sclent. Mor£e, part. Zool., 39, pi. xxvii, f. 3, 1832. 
Alpheus candei Guerin, in La Sagra’s Hist. Cuba, 2d part, vii, p. xix, pi. it, f. 9, 1857. 
Alpheus transverso-dactylus Kingsley, Bull. U. S. Geol. Survey, iv, 196, 1878. 
Rostrum a slender spine, not reaching second antennular segment. Orbital margin with a small 
spine, less advanced than rostrum; on the margin between rostrum and orbital spine a thin laminate 
