I. '08. 



36 



a. First two pairs of pereiopods 

 slender, the first either simple or 

 microscopically chelate, the second 

 with chelae of small size ; mandibles 

 with palp, and with incisor and 

 molar processes, . . . Pandalidae (p. 84). 



h. First two pairs of pereiopods not 

 both very slender, the first with 

 chelae of moderate size, although 

 occasionally smaller than those of 

 second pair ; mandibles with or with- 

 out incisor process and palp, Hippolytidae (p. 99). 



ii. Of the first pair of pereiopods, one is 

 simple, the other chelate; rostrum 

 short and unarmed ; mandibles with- 

 out palp or incisor process, . Processidae (p. 123). 



B. Eyes usually covered, at least partially, 

 by a projection of the frontal margin 

 of carapace ; first pereiopods very 

 robustly chelate, . . . Alpheidae (p. 119). 



II. Carpus of second pereiopods unsegmented, simple. 



A. First pereiopods with small chelae, 



second pair with larger and more 



robust chelate, . . Palaemonidae (p. 127). 



B. First pereiopods sub-chelate, second 



pair slender (rarely absent), minutely 



chelate or simple, . . Crangonidae (p. 134). 



For the purposes of the present paper I have not thought 

 it necessary to make use of super-families as in the scheme 

 proposed by Borradaile (1907). Certainly in the Caridea such 

 groups can at present only be regarded as hypothetical, at 

 any rate until the families themselves are more satisfactorily 

 defined. 



Family PASIPHAEIDAE. 



Of this family two genera are now known from British and 

 Irish waters. They may be distinguished thus : — 



I. Rostrum in the form of a post-frontal spine ; mandible 

 without palp ; gill formula : — 



— 



VIL 



VTTT. IX. 



X. 



XL 



XII. 



XIIL 



XIV. 



Podobrauchiae. 



Arthrobranchiae, 



Pleurobranchiae, 







fep. 

 rucl. 



1 

 1 



1 

 1 



1 



1 



J 



1 



Pasipha'e (p. 37) 



