Classification of the Decapod Crustaceans. 471 



II. Second mnxillipods witli the sixth and seventh 

 joints articuhitiiig separately on fifth. [No 

 exopodites on legs. Mastigobranchs on first 

 to fuurth pairs. First two i)air8 of good size, 

 chelate, with very long fingers and undivided 

 wrist-joints. Mandibles imperfectly cleft, 

 with palp.] 



III. Second niaxillipeds with short seventh joint, 

 usually applied as a strip to the end of the 

 sixth. 



1. Mandibles imperfectly cleft. Exopodites 



usually present on all or some legs. First 

 two pairs of le^^s substantially similar, of 

 moderate size, chelate, with undivided 

 wrist-joint. [Mastigobranchs present on 

 some legs (except LDnnocaridiiia).^ .... 



2. Mandibles either deeply cleft or simple, 



apparently owing to the loss of the cuttinyr- 



edge. No exopodites on legs (except in 



a very few cases on the first pair). First 



two pairs of legs more or less unlike. 



i. At least the basipodites of the second 



maxillfe well developed. Mandibles 



rarely simple {Latreutea &c.). Fii'st legs 



not subchelate. 



(1) First two pairs of legs slender. Fii-st 



pair simple or minutely chelate. 

 Second chelate, with wrist divided 

 into two or more joints. [Masti'''o- 

 branchs generally present on legs.] . . 



(2) First legs with both fingers movable, 



second with last joint replaced by a 

 tuft of bristles and undivided wrist- 

 ioint. [No mastigobranchs on legs.] 



(3) Inrst two pairs of legs not both slender 

 (one often very large), chelate. "Wrist 

 of second pair often subdivided. 

 [Mastigobranchs present or not.] . . 



ii. Inner lobes of second maxilla? reduced. 

 Mandibles simple. First legs often sub- 

 chelate. [.Second wrist divided or not. 

 No mastigobranchs on legs.] 



Stylodactyloida. 



H0PL0PH0n0IT>A. 



Pandaloida. 



PSALIDOPODOIDA. 



rAL.a:MONOIDA. 



Cbangonoida. 



Key to the Families of the Pasiphaioida. 



I. Rostrum small or wanting. No molar process 

 on the mandibles. Inner lobes of second 

 maxillaj and first maxillipeds reduced. Exo- 

 podites on all legs Pasiphaeidae. 



II. Rostrum well developed. Mandibles with a 

 distinct molar process. Inner lobes of second 

 maxillae and first maxillipeds not reduced. 

 Exopodites on first two pairs of legs only . . Bresiliidae. 



Key to the Families of the Iloploplioroida. 



I. Both fingers of chelae spoon-liko and ending 

 in tufts of bristles. Exopodites may be 



