260 THE VOYAGE OF H.M.S. CHALLENGER. 



" 2. The abdominal members in two sets, the three anterior pairs subnatatory, the three posterior 

 styliform." 



Of the intermediate Anisopoda, he says, " They have — 



"L Like Ampliipoda, the three posterior pairs of thoracic legs in one series, and the four 

 anterior in a different series. 



" 2. Like Isopoda, the three posterior pairs of abdominal members are not styliform, only the last 

 having this character." 



In discussing the question whether the Amphipoda or Isopoda should rank the higher, he remarks, 

 in favour of the Amphipoda, the position of the branchias on the thorax, as thoracic branchiae 

 characterize aU the higher Crustacea. On the other hand, he considers that they show 

 inferiority, by the elongated abdomen, with natatory appendages below, and by the usually 

 long antenna?, both these being jNIacroural characters. Further, the anterior set of legs 

 includes four pairs, an evidence, he considers, of less concentration of force in the cephalic 

 ganglia ; they have a less compact body, are less ajit to take to a habitat on dry land, and 

 above all, have often the two " dorsal cords " distinct between the gangUa, while in the 

 Isopods there is but a single cord. This double cord is seen in none of the higher Crustacea. 



In Tribe III. the Amphipoda (p. 805), he recognizes two types of structure, one, the Hyperidea, 

 ■with smaU, operculiform maxillipeds, large faceted eyes covering most of the large head, the 

 extremity of the abdomen broad and depressed, the natatory abdominal appendages usually 

 oval, lamellar ; " in the other type, the outer maxillipeds are elongated and palpiform, the 

 eyes are small, the head of moderate size, the abdomen, when not obsolete, narrow, and the 

 natatory abdominal ajjpendages usually slender. This second type comprises two groups. 

 In one section, the Caprellidea, the abdomen is obsolescent. In the other, the Gammaridea, 

 the abdomen is fully developed, with three pairs of natatory appendages, and as many of 

 stylets." This section embraces the typical Amphipods, the Gammari, Talitri, and the like. 



His three subtribes, Caprellidea, Gammaridea, and Hyperidea, he divides and subdivides into 

 families and subfamilies, which are defined as follows : — 



Subtribe I. Caprellidea. FamQy I. CapreUidse. — Corpus anguste elongatum, fere filiforme. 

 Antennae 2dae longitudine mediocres. [Species non parasiticae.] 



Fam. II. Cyamidse. — Corpus late depressum. Antennre 2d£e rudimentarife. [Species parasiticae]. 



Subtribe II. Gammaridea. Fam. I. Dulichidse. — Habitu Caprelloideae. Corpus lineare, 

 epimeris obsoletis. Pedes 6 postici longi, subprehensiles. Abdomen 5-articulatum. 



Fam. II. Cheluridae. — -Corpus fere cylindricum, epimeris mediocribus. Abdomen abnormale, 

 segmentis 4to Stoque coalitis et oblongis, stylis inter se valde dissimUibus. 



Fam. III. Corophida:\ — Gressoriae, pedibus partim lateraliter porrectis. Corpus plus minusve 

 depressum, sive latum sive lineare, epimeris perbrevibus, interdum obsoletis. Abdomen 

 forma appendicibusque normale. Antennje saepe pediformes. 



Fam. IV. Orchestidae. — Saltatorije, pedibus nuUis lateraliter porrectis. Corpus compressum, 

 epimeris magnis. Abdomen appendicibus normsile. Antennae non bene pediformes. Styli 

 caudales Imi 2dique biramei; 3tii simpHces, brevissimi et ultra 2dos non prolon^ati. Man- 

 dibulae non palpigera\ Maxilla Imaj palpo sive parvulo et 1-articulato sive obsoleto 

 instructje. 



Fam. V. Gamniarida;. — Saltatoria:- vel natatoriee, jjedibus nullis lateraliter porrectis. Corpus 

 sspius compressum, rare subdepressum, epimeris sive magnis sive parvis. Styli caudales 

 laxiores, duobus altimis oblongis srepiusque ultra 2dos prolongatis, raro simplicibus. 

 Mandibulaj saepissime palpigera;. Masillw Imae palpo 2-3-articulato (rarissime 1-artioulato) 

 instructap. 



Subtribe III. Hyperidea. Fam. I. Hyperida;-. — Antennfe 2dK exsertas. Abdomen in ventrem 

 se non flectens. Pedes 5ti 6tique Tmique forma lougitudineque mediocres, 5tis 6tisque 

 non percrassis nee prehensililms. 



