THE BRACHYURA AND MACRURA OF PORTO RICO. 
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Suborder MACRURA. The Shrimps and Lobsters. 
Key to the Porto Rican families of the suborder Macrura. 
A. Body not compressed. Rostrum depressed, often wanting. First abdominal segment shorter and narrower 
than the following. Abdominal appendages- not oar-shaped. The articulation between carpus 
and propodus at two fixed points. 
B. Third pair of feet not chelate. 
C. PI eon with segments not overlapping Tribe Thalassinidea 
D. First pair of trunk-legs unequal Family Caluanassim: 
D'. First pair of trunk-legs subequal Family Axiidte 
C'. Pleon with segments overlapping Tribe Loricata 
D. Carapace flattened; external antennae flat, short, squamiform Family ScYhLARiDiE 
D'. Carapace subcylindrical; external antennae very long and rigid Family Palinuridas 
B'. Third pair of feet chelate Tribe Ilomaridea; Family HoMARlDiE 
A'. Body more or less compressed. Rostrum usually compressed. Abdominal appendages oar-shaped. Articu- 
lation between the carpus and propodus at only one-fixed point. 
B. The epimera of first abdominal segment not covered by those of second. Third pair of feet chelate, usually. 
C. Three pairs of chelae nearly equal and not very strong Tribe Penxidea; Family Penteid^e 
C'. Third pair of chelae considerably stronger than the first and second pairs Tribe Stenopidea; Family Stenopid/E 
B'. The epimera of first abdominal segment covered by those of the strongly developed second segment. 
Third pair of feet not chelate Tribe Caridea 
C. Carpus of second pair of feet subdivided into few or many segments. 
D. Eye-stalks short and usually more or less covered by carapace. . ; Family Alpheim: 
D'. Eye-stalks not covered by carapace. 
E. First pair of feet more or less chelate. 
F. Rostrum small. First pair of feet moderately strong Family Lysmatid;e 
F'. Rostrum of important size. First pair of feet small Family Hippolytida: 
E'. First pair of feet simple Family Pandalid.® 
C'. Carpus of second pair of feet not subdivided. 
D. Rostrum long, usually dentate Family Palasmonidje 
D'. Rostrum small or wanting. 
E. First two pairs of feet subequal and similar. 
F. Fingers of first and second pairs of feet spoon-shaped. Mandibles without palp Family Atyid.® 
F'. Fingers of first and second pairs of feet not spoon-shaped. Mandibles with palp Family Pasiph.eid,e 
E'. Second pair of feet much stronger than the first. 
F. Third maxillipeds pediform Family Pontoniidje 
F'. Third maxillipeds with the third segment strikingly broad Family Gnathophyllidje 
Tribe THALASSINIDEA. 
Carapace short, compressed, and marked with two longitudinal sutures. Rostrum small or 
wanting. Both pairs of antennae elongated and furnished with long peduncles, those of the outer pair 
five-jointed and usually without a scale. First pair of feet more or less chelate; second pair often 
chelate; third pair always simple. Last segment of the thorax movable. Abdomen long, the segments 
not overlapping, the side plates feebly developed. Swimming-fan well developed. Branchiae variable. 
Family CALLIANASSIDAi Dana, 1852. 
Rostrum minute or absent. Eyes small; eye-stalks flattened, sometimes laminate; corneae not 
terminal. First pair of trunk-legs unequal, perfectly or imperfectly chelate, the third and fourth pairs 
simple, the others variable. In the large cheliped, the carpus is formed as if it were a continuation of 
the propodus; carpus and propodus much wider than merus. Uropods and telson usually broad. 
Branchiae filamentous, with the filaments sometimes compressed. 
Key to the Porto Rican genera of the family Callianassidse. 
A. Second pair of pleopods differing from following three pairs; pleopods fringed with fine hairs. 
B. Merus and ischium of maxillipeds dilated, wider than the following joints Callianassa 
B\ Merus and ischium of maxillipeds not wider than the propodus, which is dilated Glypturus 
A'. Second pair of pleopods like the following three pairs, all of these are fringed with articulated membra- 
nous filaments Callianidea 
