8 BULLETIN 152, UNITED STATES NATIONAL MUSEUM 



SYSTEMATIC DISCUSSION 



Order DECAPODA 



Suborder REPTANTIA 



Tribe BRACHYURA 



Subtribe BRACH'iiGNATHA 



Superfamily BRACHYRHYNCHA 



KEY TO SUBTRIBES OF THE TRIBE BRACHYURA 2 



A'. Anterior thoracic sterna very broad, posteiior thoracic sterna narrow and 

 keel-like. Posterior thoracic epiiBera largely exposed by reduction of the 



branchiostegite Subtribe Gymnopleura.^ 



A^. Anterior thoracic sterna not unusually broad, posterior thoracic sterna not 

 keel-like. Posterior thoracic epimera covered by the branchiostegite. 

 B'. Mouth field (endostome) prolonged forward to form a gutter. Last pair 

 of legs normal or abnormal. Female openings generally sternal. First 

 abdominal limbs wanting in female. Gills few. 



Subtribe Oxijstomata. 

 B2. Mouth field roughly square. 



C^ Last pair of legs abnormal, dorsal. Female openings coxal. First 

 abdominal limbs of female present. Gills usually many. 



Subtribe Droviiacea. 

 C'K Last pair of legs normal, rarely reduced, not dorsal, except in 

 Cymopolia and Retropluma. Female openings sternal. First 

 abdominal limbs of female wanting. Gills few. 



Subtribe BRACHYGNATHA. 



KEY TO SUPERFAMILIES OF THE SUBTRIBE BRACHYGNATHA 



A'. Fore part of body narrow, usually forming a distinct rostrum. Body more 

 or less triangular. Orbits generally incomplete. 



Superfamily Oxyrhyncha. 

 A^. Fore part of body broad. Rostrum usually reduced or wanting. Body 

 oval, round, or square. Orbits nearly always well inclosed. 



Superfamily BRACHYRHYNCHA. 



KEY TO FAMILIES OF THE SUPERFAMILY BRACHYRHYNCHA 



A'. Orbits formed, but more or less incomplete. Second autennal flagella, when 

 present, long and hairy. Rostrum present. Body elongate-oval. Fore 

 edge of mouth indistinct Family EXJ1B.Y ALIDAE^ Cory stidae. 



A^. Orbits complete (though fissures maj' remain), except in the Mictyrinae, 

 where the eyes are almost or quite unprotected. Body rarely elongate- 

 oval. Rostrum often wanting. Second antennal flagella usually short, 

 not hairy. 



2 The keys are for the most part from Borradaile's On the Classification of the Decapod Crustaceans, Ann. 

 Mag. Nat. Hist., ser. 7, vol. 19, 1907, pp. 477^83. The names in the right hand margin which are printed in 

 capitals indicate the families and higher divisions treated of in this volume. 



' Bourne, The Kaninidae, in Journ. Linn. Soc. London, Zool., vol. 35, 1922, p. 55. 



