No. 393.] MORTH-AMERICAN INVERTEBRATES. 713 
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KEY TO THE GENERA OF CARIDEA.! 
Body usually cylindrical, elongate; antennæ long; abdomen large, 
usually extended, and bearing, as a rule, six pairs of feet 
(pleopoda), the sixth pair, together with the telson, forming a 
caudal fin MACRURA 2 
Body depressed ; antennæ sntall abdómen sitiat, Da folded under the 
cephalothorax ; no caudal fin form ; BRACHYURA 
Last pair of thoracic feet normal . : ee 
2. Last pair of thoracic feet reduced and ERT in peatilivs 
p oe u 
unr p 
Pon n 
II. 
— me 
9 OPS RSS Sere 
ANOMURA (pars) 
Carapax with two longitudinal dorsal sutures ; antennal scale small or 
lacking; cervical suture frequently present THALASSINIDEA, 
. Longitudinal sutures lacking; cervical or on present; carapax 
TACID 
united in front to epistome . AS EA 
. Carapax not united to epistome, sutures patie : Akeia scale large 
RIDEA 4 
Not more than two pairs of feet chelate 
x 5 
. Three anterior pairs of feet chelate PENEIDA 28 
Mandibles slender, incurved, not SS or r bifid at the tip; no man- 
dibular palpus (Fig. 11) . CRANGONID& 6 
Mandibles stout, crown broad, dilated (Fi ig. b . ATYIDÆ 14 
Mandibles with the crown deeply bifid (Fig. 38) PALÆMONIDÆ 17 
. First pair of feet the stouter, subchelate (Fig. 1 a); i.e., the movable 
finger closing on the palm COR 7 
First pair of feet the stouter ; chelate s LYSMATINZ I0 
Second pair the larger . ee. GNATHORRYLEINE (extralimital) 
Second pair of feet chelate : ; ` . : 8 
Second pair of feet not chelat . . . Sabian 36 
Second pair of feet nue rostrum Gite š . Paracrangon 39 
Branchiz five on either side . : . . : : : v8 
Branchiz seven on either side . oo e . Pontophilus 37 
Rostrum short, eyes free. . : Crangon 29 
Rostrum obsolete, eyes nearly convened s : Necterangon n 
Rostrum long ‘ : 
Rostrum short, ditenn bfageliste à i : Tae a 
External maxillipeds with exopodite .  . -> ; ee 
. External maxillepeds without exopodite ‘ : . Tozeuma 42 
Carpus of second pair triannulate . : : i ; D 
. Carpus of second pair multiarticulate . . . Hippolysmata 40 
. Carapax with a median dorsal spine . : . . Latreutes 43 
1 The American Naturalist will undertake to determine and return any speci- 
mens that cannot be placed in the keys, and solicits correction and criticism for 
future revision. 
