50 U.S. NATIONAL MUSEUM BULLETIN 271 



Diagnosis of the Basic Marine Gammaridean 

 (Many Mariae Gammaridae) 



Figures 1, 2 



Accessory flagellum well developed, with four or more articles. 

 Primary flagellum of antenna 1 not basally conjoint. 



Mouthpart field quadratiform from lateral view. Each mandible 

 with 3-articulate palp, article 3 longer than article 1; molar present, 

 with grinding surface composed of ridges and teeth (=triturative). 

 Lower lip with principal lobes undivided (unnotched) and not widely 

 separate. Each maxilla 1 bearing inner lobe, outer spinose lobe, and 

 strong unflexed palp of two articles. Each maxilla 2 with two well- 

 developed, setose lobes. Each side of maxUlipeds with large inner 

 (proximal) lobe and outer (distal) lobe, and 4-articulate palp, article 4 

 claw-shaped (unguif orm) . 



Gnathopods well developed and subchelate ("powerful"), non- 

 lysianassid. Gnathopod 2 larger than gnathopod 1 in male, gnathopod 

 1 never larger than 2 in female, article 3 of gnathopod 2 short. Article 4 

 of pereopods 1-2 not extensively elongate. Pereopods 3-5 of con- 

 gruent structure and successively slightly longer. 



Three pairs of large and subequal uropods present, all biramous, 

 rami subequal in length, lanceolate. Peduncle of uropod 3 not elongate. 

 Telson deeply cleft, of medium length. 



Coxae forming elongate, rectangular plates with quadrate or 

 rounded distal edges, coxae 1-4 of uniform shape or slightly increasing 

 in size consecutively, coxa 4 excavate posteriorly. 



All body segments free. Metasome only as long as last five pereonites 

 combined. Head subcuboidal, not "massive," rostrum small. 



