AN UNDIVIDED WRIST 239 



cwrinatus of S. I. Smith, who says that the basal joint of 

 the first antenna is ' furnished externally with a large 

 lamellar process terminating anteriorly in an acute angle 

 in front of the eye,' a description ill-suited to the epithet 

 rudimentary. 



Legion 3. — Monocarpinea. 



The wrist, or fifth joint of the second pair of trunk-legs, 

 is not subdivided, and generally the chelse of this pair are 

 larger than those of the first. 



Spence Bate arranges in this group eleven families — 

 the ThalassocaridiB, Atyidee, Pontoniidse, Caricyphidae, 

 Acanthephyridse, Palsemonidae, Nematocarcinidae, Tropio- 

 caridaB, Stylodactylidae, Pasiphaeidee, Oodeopidae, among 

 which the first differs from all the rest by having the first 

 pair of trunk-legs simple, and the last differs from all the 

 rest by having the second pair simple. The Tropiocaridge 

 do not seem to deserve a separate existence, without 

 further consideration . 



Family 1. — Thalassocaridce. 



The first trunk-legs are simple, the second chelate. 

 Three genera are assigned to the family, one of them, 

 Diaphoropus, Spence Bate, 1888, founded on what ' is 

 evidently the immature condition of some undetermined 

 form.' 



Thalassocdris, Stimpson, 1860, takes the place of 

 Regidus, Dana, 1852, the latter name being pre-occupied. 

 The species as yet known belong to the Pacific, and are 

 regarded as a link connecting the Pandalidse with the 

 Palsemonidas. 



Family 2. — Atyidic. 



The carapace is dorsally smooth, with flattened ros- 

 trum ; the scale of the second antennse short. The man- 

 dibles have a molar process and cutting edge, but no ' palp.' 

 The third maxillipeds are f jur-jointed and pediform. The 

 first and second trunk-legs are chelate, with spoon-shaped 

 fingers. The telson is flattened, truncate. 



