426 L. A. BORRADAILE. 



to those applied to the spider crabs, Oxyrhyncha and Maioidea. The group thus formed 

 presents a series of families, long and varied indeed, but neither more numerous nor more 

 diverse than, for instance, those included in the Caridea (Eukyphotes). 



With regard to the position of the remarkable family Hymenosomidae I am in agree- 

 ment with Ortmann in provisionally placing them among the Oxyrhyncha. The genus 

 Catoptnis A. M.-Edw., 1870 (= Goniocaphyra de Man, 1887), which I have already' proposed 

 to make the type of a subfamily of the Portunidae, I shall for the present continue to 

 keep in that position, in spite of the fact that, if Catoptrus seems clearly related to Carupa 

 and perhaps also to Caphyra among the swimming crabs, it has hardly less clear resem- 

 blances to Libystes and Carcinoplcuc among the Gonoplacidae. The Hapalocarcinidae should, 

 I believe, be placed somewhere among the Brachyrhyncha but, in view of their exceedingly 

 doubtful affinities, are not included in the key given below. For the same reason the 

 family Trichiidae, which should probably be established for Trichia de Haan is also left 

 unmentioned. Lastly, I have followed Alcock in placing Palicus near the Catometope families. 

 The accompanying table gives the classification of the Brachyura, as it will stand with the 

 changes proposed above, and the characters on which it depends are summarised by means 

 of a series of keys. 



Suhtrihes of the Brachyura. 



I. Fore edge of the mouth-field (endostonie) prolonged forwards to form a gutter. [Last pair of 



legs normal or abnormal. Female opening generally sternal. First abdominal limb of female 

 wanting. Gills few.] Oxystomata-. 



II. Mouth-field roughly square. 



A. Last pair of legs abnormal, dorsal. Female genital opening coxal. First abdominal limb of 

 female present. Gills usually many. Dromiacea'. 



B. Last pair of legs normal, rarely reduced, not dorsal, except in Palicus and Ptenoplax. 

 Female genital opening sternal. First abdominal limb of female wanting. Gills few. 

 Brachygnathu . 



Legions of the Brachygnatha. 



I. Fore part of body narrow, usually forming a distinct rostrum. Body more or less triangular. 



Orbits generally incomplete. Oxyrhyncha". 



II. Fore part of body broad. Rostrum usually reduced or wanting. Body oval, round or square. 

 Orbits nearly always well enclosed. Brachyrhyncha. 



Families of the Brachyrhynclw,. 



I. Orbits formed but more or less incomplete. [Antennal flagella, when present, long and hairy. 



Rostrum present. Body elongate-oval. Fore edge of the mouth indistinct.] Corystidae. 



II. Orbits complete (though fissures may remain), except in the Mictyrinae, where the eyes are 

 almost or quite unprotected. [Body rarely elongate-oval. Rostrum often wanting. Antennal 

 flagella usually short, not hairy.] 



' Proc. Zool. Soc. 1900, pp. 578, 799. ' For key see the article on the group. 



