occurring on the Norwegian Coasts. 327 



nearer or more distant affinities, but without grouping them 

 in subfamilies ; nevertheless, in noticing the genera esta- 

 blished as typical of the latter, I will touch upon such points 

 as I believe may serve to elucidate the nearer relationships of 

 the groups. 



In the systematic arrangement of the Amphipoda I have 

 not only taken into account the form of the legs and tail, 

 but have also especially sought to obtain systematic characters 

 from other equally important and more occult organs, such as 

 the parts of the mouth and the ovigerous and respiratory 

 lamella?. Undoubtedly the structure of the buccal organs has 

 long since been employed in systematic arrangement, as the 

 absence or presence of palpi on the maxilla? or mandibles and 

 the number of joints in the maxillipedes have been cited as im- 

 portant characters ; but I maintain that the form of the inner 

 lamella on the first pair of maxilla? and its border of hairs 

 furnish specially characteristic marks. Moreover the border- 

 ing of teeth and hairs which occurs at the upper end of the 

 oesophagus is of importance. In this preliminary memoir, how- 

 ever, I have not taken notice of this last character (although 

 my investigations already made have quite convinced me of 

 its importance in a systematic point of view) , partly because it 

 cannot be described without greater prolixity than this memoir 

 permits, and partly because its investigation is difficult. The 

 form of the ovigerous lamella?, and their relative size and 

 relations to the respiratory lamella?, are also very essential ; 

 but in this memoir I have noticed only those which are 

 attached to the fourth pair of legs. It must be remarked, 

 however, that these do not always maintain the same size 

 (as some observers have stated), but are smaller when the 

 females do not employ them for the protection of the eggs 

 or young. I may here also call attention to the double arma- 

 ture of teeth which the males of many species possess in con- 

 tradistinction to the females, the mandibles being furnished 

 on the inner surface with a toothed point, whilst the rows 

 of spines and masticatory tubercles are sometimes doubled. 

 At the same time the outer lamella of the first pair of maxilla? 

 has, besides the strong armature of teeth at the apex, another, 

 corresponding one on the inner surface ; their palpus shows a 

 similar construction to that of the second pair of maxilla?. 

 This I have found to be the case in species of the genera 

 Orchestia, Allorchestia, Anonyx, Ampelisca, Haploops, Dexa- 

 mine, Gammarns (dentatus, Kr.), Ampliitopsis, AcantkonotuSj 

 Gammaropsis (anomalus^ H. R.), and in certain Caprellida? 

 — for example, in the genus JEgina. 



As Bruzelius's memoir is a complete monograph of the 



25* 



