428 L. A. BORRADAILE. 



A. Carpopodite of 3rd maxilliped articulates at or near tlie antero-internal angle of the mero- 

 podite. [Body usually round or transversely oval. Male opening nearly always coxal.] 



1. Legs more or less distinctly adapted for swimming. [Antennules fold slanting or trans- 

 verse. Usually a small lobe on the inner angle of the endopodite of the 1st maxilliped'.] 

 Poriunidae. 



2. Legs not adapted for swimming. Or, if so modified, tlien the vas deferens opens sternally 

 or runs in a sternal groove (certain Macrophtludmus and Libystes). Inner lobe on the 

 endopodite of the first maxilliped wanting I 



a. Freshwater crabs with the branchial region much developed and swollen. [Body often 



squarish, but male opening coxal.] Potamonidae. 



b. Marine crabs, with the branchial region not greatly swollen. 



i. Antennules fold lengthwise. 



a. Carapace subcircular. Antennal flagella either long and hairy or wanting. Alele- 



ci/clidae^. 



/3. Carapace broadly oval or hexagonal. Antennal flagella present, short, not hairy. 

 Cancridae^. 



ii. Antennules fold slanting or transversely. 



a. Body usually transversely oval. Male openings rarely sternal. Not sharply separated 

 from the following family. Xanthidae*. 



p. Body usually square or squarish. Male ducts open on the sternum or, if coxal, 

 pass along a groove in the sternum. Not sharply separated from the foregoing 

 family. Gonoplacidae. 



B. Carpopodite of 3rd maxilliped does not articulate at or near the inner angle of the 

 meropodite. [Body usually square or squarish. Male opening sternal, except in Pienoplax, 

 where the duct passes along a sternal groove to the coxopodite.] 



1. Small symbiotic crabs with very small eyes and orbits. Body usually more or less 



rounded. Phmotheridae. 



2. Free-living crabs with eyes not specially reduced and usually a square body. 



a. Last pair of legs dorsally placed and weaker than the others. [Interantennular septum 

 very thin. No distinct epistome. Exopodite of 3rd maxilliped not hidden.] 



i. Front narrow. Female opening in normal position, 3rd maxillipeds subpediform, not 

 covering the mouth. Ptenoplacidae. 



ii. Front moderately broad. Female openings on the sternal segment corresponding to 

 1st pair of walking legs. 3rd maxillipeds cover the mouth ventrally and have a 

 very small meropodite. Palicidae. 



1 A key to the subfamilies of the Portuaidae will be found structure. lu Cardiosoma the outer angle is divided from the 



in the Proc. Zool. Soc. 1900, p. 577. The name Catoptrinae main part of the plate, thus leaving a large inner lobe. This 



should be substituted for Goniocaphijrinae, Milne-Edwards' again is probably not the same structure as that in the 



name Catopirus having priority of Goniofaphyra de Man. Portunidae (Fig. 110 b). 



^ I make this statement on the authority of Ortmann ■' For key to subfamilies see below. 



(Zool. Jahrb. ix. toe. cit.). Uca {^Gelasimus) and many ■> A key to the subfamilies of the Xanthidae will be found 



other genera have a small lobe on the inner side of the above on p. 238 of Pt. in. in the article on that family, 

 endopodite, but this is not at the angle and is a different 



