MARINEi GAMMARIDEADNT AMPHIPODA 289 



Leucothoidae 



Figures 113, 114 



Diagnosis. — Accessory flagellum vestigial, 1- or 2-articulate, very 

 small; mandible lacking molar; outer plates of maxilliped very small, 

 probably never larger than inner plates; telson entire; gnathopod 1 

 carpochelate. See Anamixidae, Sebidae, Amphilochidae, Cressidae, 

 Thaum atelsonid ae . 



Description. — Body lacking dorsal processes; accessory flagelkim 

 vestigial; epistome probably always produced in front; upper lip 

 probably always asymmetrically incised; mandibles lacking molar, 

 palp 1- or 3-articulate; maxillae basic; maxilliped with very small 

 outer plates, partially fused inner plates and long slender palp; 

 gnathopod 1 carpochelate, immovable finger long and narrow, gnatho- 

 pod 2 larger than 1, subchelate, article 5 elongate and guarding 

 article 6 posteriorly; coxae variable; uropod 2 shortened; uropod 3 

 with styliform rami, peduncle elongate, rami not longer than peduncle; 

 telson entire, not longer than peduncle of uropod 3. 



Relationship. — The Anamixidae lack maxillae and recognizable 

 mandibles. 



The Cressidae, Thaumatelsonidae, and Stenothoidae have unira- 

 mous third uropods and subchelate first gnathopods. 



The Sebidae have uniramous third uropods and chelate second 

 gnathopods. 



Key to the Genera of Leucothoidae 



1. Coxa 2 covering most of coxa 1 (fig. 113c), mandibular palp l-articulate 



(fig. 113/) Leucothoides 



Coxa 1 not concealed, mandibular palp 3-articulate (fig. 113e) 2 



2. Coxa 2 very short, broader than long, acute anteriorly (fig. 1136). 



Leucothoella 

 Coxa 2 at least as long as broad, rounded below and anteriorly (fig. 113a) . . 3 



3. Outer plate of maxilliped reaching less than halfway along palp article 1 



(fig. 114d) Leucothoe 



Outer plate of maxilliped reaching almost to end of palp article 1. 



Paraleucothoe 



Genera of Leucothoidae 



Leucothoe Leach 



Leucothoe Leach, 1814a. — Stebbing, 1906. 

 Cuvieria Leach, 1814a (nomen nudum). 

 Lycesta Savigny, 1816. 



Type-species: Gammarus spinicar pus AhildgaSiTd, 1789 (monotypy 

 and subsequent synonymy). See Sars, 1895. 



