occurring on the Norwegian Coasts. 331 



the head, eyes, antennas, and abdomen, and partly also in the 

 outer lamella of the maxillipedes, which is opercnliform ; but 

 here there are palpi, which are wanting in the Hyperidas. On 

 the whole, the parts of the mouth in this animal are peculiar, 

 and appear as if intended for sucking. In some respects it 

 approaches the Orchestidas, but lias also much in common with 

 the genera Opts and Anonyx among the Gammarida3 in the 

 structure of its antennas and feet. 



Tribe III. Gammaeid^e : — 



Family I. Orchestid.33. — None of the characters which are 

 proposed for this family belong to it exclusively, or are con- 

 stant in all its forms. By the long superior antennas and the 

 well-developed claw on the palpi of the maxillipedes in AUor- 

 chestia^ this family approaches the Gammaridae, from which, 

 again, it is not clearly separated by the want of mandibular 

 palpi, as these are also wanting, for example, in the genus 

 Dexamine. Acanihonotus and Stegocephalus possess a short 

 maxillary palpus like that of AUorchestia. Again, the pecu- 

 liar form of the abdomen is not exclusively characteristic of 

 this family, as it also occurs in several genera of the family 

 Corophidas. The two genera of this family which occur on 

 our coasts differ from the other Amphipoda, however, by the 

 series of spines on the mandibles. This is formed by long, 

 thick, but flexible, and strongly ciliated hairs, whilst those of 

 all other Amphipoda examined by me consist of simple denti- 

 culated spines, or of spines divided at the apex. In the struc- 

 ture of the inner lamella of the first pair of maxillae (which is 

 long, narrow, and furnished at the end with two long, ciliated 

 hairs) the family much resembles the genera A no ny x and Oj)is } 

 which it also resembles in having the ovigerous lamellae longer 

 and much narrower than the respiratory lamellas, and at the 

 same time furnished with long, but not, approximated, hairs. 

 In both our genera of this family there is in the males the 

 peculiar double armature of teeth, which is wanting in the 

 females. In AUorchestia Nilsonii this is particularly distinct 

 on the mandibles and first pair of maxilla?. 



Family 2. G-ammaridae. — For this family it is still more dif- 

 ficult to lay down definite limits. Neither Milne-Edwards's 

 statement that his Crevettines marcheuses, which nearly coin- 

 cide with Dana's family Corophidas, are distinguished from 

 the Crevettines sauteuses by their less compressed body and 

 their small epimera, and by the three hinder pairs of abdo- 

 minal legs being furnished with " lames natatoires," and 

 not formed as a jumping-apparatus, nor Dana's statement 

 that his Cbrophidas have " pedes partim lateraliter porrecti," 



