MARINE GAMMARIDEAN AMPHIPODA 521 



fossorial. Associated with the habit of burrowing, often referring to the exces- 

 sively spinose or setose condition of appendages used for burrowing by Gam- 

 maridea; especially applicable to Haustoriidae, Oedicerotidae, Phoxocephalidae 

 with some setae of articles 4-6 of pereopods 3-5 more than half as long as 

 those articles; and some spines in groups forming submarginal rows perpendicu- 

 lar to margins; long setae also occur on "filter" feeders such as Ampeliscidae. 



galeate. Descriptive of the helmet-shaped heads of various oedicerotids and 

 synopiids. 



gamopod. A gnathopod; referring to the use of gnathopods for grasping members 

 of the opposite sex during amplexus. 



geniculate. Permanently bent, usually in reference to the flexeda ntennae of some 

 haustoriids, or the outer lobes of maxilla 2 in some stegocephalids in which the 

 bend occurs between articles; or applicable to bent palps of maxilla in Hyper iop- 

 sidae in which the bend occurs on one article. 



gnathopod. One member of the first two pairs of free thoracic appendages; these 

 appendages differ in function and usually in appearance from following pereo- 

 pods; often called pereopods. 



incisor. The apical portion of the mandible usually formed into a toothed chewing 

 edge or untoothed chopping plate. 



joint. The juncture between two articles of an appendage. 



labrum. (See upper lip.) 



lacinia mobilis. An articulated accessory plate proximal to the mandibular 

 incisor, often absent or missing on either left or right mandibles, occasionally 

 indistinguishable from a spine of the spine-row. 



low lip (labium). A fleshy complex posterior to the mandibles, always composed 

 of at least one pair of lobes (outer), often with a medioproximal pair of inner 

 lobes; the lateroproximal ends of the outer lobes are often attentuated as alae 

 and are denoted as mandibular lobes (fig. 2g). 



mandible. The anterior movable appendage of the buccal group; usually composed 

 of a body bearing a distal incisor, a lacinia mobilis, spine row, molar, and 

 3-artculate palp (fig. 2/). 



massive. A term applied to the heads of Synopiidae and Oedicerotidae; head 

 as long as pereonites 1-3 combined and as tall as or taller than long (length 

 not including rostrum). Heads of Ampeliscidae and Phoxocephalidae are 

 elongate but not massive; heads of Acanthonotozomatidae are as tall as long 

 but are not as long as pereonites 1-3 combined. 



maxilla 1. A pair of cephalic appendages posterior to the lower lip; for taxonomic 

 purposes only three portions of each member are named: the medial lobe 

 (plate) usually bearing marginal setae, the lateral and larger lobe (plate) 

 bearing terminal spines, and, attached to the outer lobe, a palp usually com- 



' posed of two articles but occasionally absent (fig. 2g). 



maxilla 2. A pair of cephalic appendages posterior to maxilla 1; for taxonomic 

 purposes each member recognized as a pair of lobes (plates) medial and lateral, 

 usually strongly setose (fig. 2i). 



maxillipeds. The posteriormost pair of "cephalic" appendages, representing 

 the primitive first thoracic segment now amalgamated with the head but in 

 amphipod taxonomy not included in the sequential numbering of thoracic 

 appendages; for taxonomic purposes recognized as a pair of basally amalga- 

 mated appendages, each member composed of a proximal (inner) plate, a distal 

 (outer) plate, and a palp of four articles, rarely reduced to 3 or 2 articles or 

 absent (fig. 2^. 



merochelate. Immovable finger of prehensile appendage occurring on merus 

 (article 4); example; gnathopod 1 of Aora. 



