MARINE GAMMARIDEAN AMPHIPODA 473 



Maxilla 1 with small 2-articulate palp ; article 4 of maxillipedal palp 

 a vestigial bud or absent; gnathopod 1 of both sexes simple or poorly 

 subchelate, male gnathopod 2 larger than 1, subchelate, article 5 not 

 produced between articles 4 and 6, female gnathopod 2 small, mitten- 

 shaped; uropod 3 lacking inner ramus; telson entire or slightly notched. 

 Species: 39, circum tropical, amphiboreal terrestrial (some beach- 

 hoppers) . 



Thaumatelsonidae 



Figures 170, 171 



DiAGNOsis.^ — Accessory fiagellum absent or vestigial; mandibular 

 molar evanescent; coxa 1 very small or absent, always partially 

 covered by following coxae; coxa 4 large, shield-like, not excavate 

 posteriorly; uropod 3 uniramous; outer lobes of maxilliped vestigial; 

 telson entire, greatly thickened dorsoventrally; urosomal segments 

 coalesced or partially so ; article 2 oj jpereopod 3 (and 4-5) linear. See 

 Stenothoidae, Cressidae, Pagetinidae, Leucothoidae, Anamixidae, 

 Amphilochidae. 



Description. — Rostrum inconspicuous; accessory fiagellum absent 

 or vestigial; body smooth or pleon with dorsal carinae; coxa 1 small 

 or absent, hidden by following coxae; coxa 4 large, shield-like, not 

 excavate posteriorly; upper lip probably incised; mandible Avith 

 evanescent molar, palp present or absent; lower lips unknown; maxilla 

 1 with 2-articulate palp; maxilla 2 normal; maxilliped slender, outer 

 plates small or vestigial; gnathopods moderately powerful, subchelate 

 or chelate; uropod 3 uniramous, the ramus 2-articulate; telson greatly 

 thickened dorsoventrally; urosomal segments coalesced or partially 

 so, or urosomite 1 often with large dorsal process covering remainder 

 of urosome dorsally. 



Relationship. — The Stenothoidae have distinct urosomal segments 

 and unthickened telsons. 



The Cressidae have the unthickened telson fused with urosomite 3. 



Parathaumatelson Gurjanova (1938) is synonymized with Pseudo- 

 thaumatelson Schellenberg (1931). 



Key to the Genera of Thaumatelsonidae 



1. Gnathopod 2 chelate (fig. \llj) Prothaumatelson 



Gnathopod 2 subchelate (figs. 171/i,z) 2 



2. Palp of mandible 1-articulate or absent 



Pseudothaumatelson ( = Parathaumatelson) 

 Palp of mandible 3-articulate Thaumatelson 



