Structure uf the Mouth in Suck in*/ Crustacea. 205 



MjTiopoda. The protuberance by ^vllicIl their mandibles 

 articulate with tlie pahite has been observed by Latrdlle 

 (Rijjjjne Auiiiial, ISliO, iv. p. 3.'J5), but he describes it aa " un 



f)etit appondice en forme de ^mlpe," Dr. Meiaert, however, 

 las rii^htly interpreti'd it as lui articular condyle in his paper, 

 '' ^lyriajKKla Musa-i llauniensis" (Naturliist. Tidsskr. ser. 3, 

 vii. p. II, and the first note). 



The TrochalognatheAmphipoda form a closely grouped divi- 

 sion, witii only two princij)al types, Lysianassa (or Anonyx) 

 and Opis ; but recent authors on the English and northern 

 fauna, esj)ecially Spence Bate, Westwood, and Axel Boeck, 

 have subdivided them into a great number of small genera. 

 The ditlereiiees a.s to the shape and armature of the oral 

 limbs are insignificant, and mostly indicated already in 

 Krciyer's careful description of the northern species (Naturhist. 

 Tidsskr. ser. 2, i. ana ii.), and in his figures in the great 

 French work ' Voyages de la Commission scientifique du Nord 

 en Scandinavie, en Laponie, au Spitzberg et au Fero pendant 

 les ann«5es 1838-1840 sur la corvette la Recherche,' Crustac<?s, 

 pis. 13-18. He has in several instances observed the condylu3 

 palatinus of the mandible, describing it as a " conic prolonga- 

 tion of the grinding-tooth ;" the var^^ing length of that piece 

 in front of the palpus which carries the condyle is expressed 

 by him and later authors by saying that the palpus is inserted 

 more or less forwardly on the mandible. He indicates, further- 

 more, correctly the different development of the lower corner 

 of the outer lobe, as well as that the terminal face of the 

 grinding-tooth in most species is somewhat larger than in 

 Anonyx lageyia^ often transversely grooved, and furnished with 

 short pectinate appendages. Finally, Krbyer has had a true 

 estimate of the systematic connexion between these Amphi- 

 poda: he says {I.e. ii. p. 55), "The genera ^1ho«_?/.c and Opis 

 appear to me to offer so many differences from the ordinary 

 type of Amphipoda as expressed in Amphithoey Gammaru^y 

 &c., that in my opinion they might properly form a separate 

 little group or subfamily in this order." 



Just as the Eleutherognathe Amphipoda correspond to 

 Onisci amongst Isopoda (the term Onisci being understood as 

 defined in the former part of my paper, vol. iv. p. 183 *), 

 thus the Trochalognathe Amphipoda correspond exactly to 

 Cfrolancr as characterized in the same place. Their habit of 

 working about in the sand of the bottom, their jx)wer and 

 endurance in swimming, their savage behaviour even to one 

 another, their voracity as carrion-eaters, and the part which 



• Ami. ct Mag. Niil. liist. i 6cr. i. pp. 7, 8. 



