GENUS MYSIS. 335 



anterior part of the thorax, the two sides bent downwards and in- 

 wards so as to be applied against the base of the feet ; anteriorly it 

 becomes very narrow, and terminates in a short flattened rostrum. 

 Eyes large, short, with the base hidden under the anterior mar- 

 gin of the carapace. Abdomen very slender, tapering, elongated, 

 nearly cylindrical. Tail as in the macrourous DECAPODA. 



No distinct branchial apparatus has as yet been observed 

 in this remarkable genus ; and, as is observed by Dr. Milne 

 Edwards, " The only appendage which appears to be so 

 modified in its structure, as to become more adapted than 

 the rest of the body to serve the purposes of a respiratory 

 organ, is the lash of the first pair of pedipalps, which in 

 other respects are similar to those found in numerous spe- 

 cies possessed of branchiae." It is, however, not at all im- 

 probable that this may be the true organ of respiration. 



The development of the young in this genus, as well as 

 their anatomy generally, has engaged the attention of the 

 late Mr. J. Vaughan Thompson, and a very elaborate 

 monograph of their structure will be found in his " Zoolo- 

 gical Researches," to which the reader is referred for full 

 information. 



The affinities of the family Mysidae, are very incorrectly 

 indicated by the position which Dr. Milne Edwards has 

 assigned them amongst the Stomopoda. In almost all the 

 essential points of structure they are certainly more nearly 

 allied to some of the Dccapoda ; but as they are also re- 

 mote even from these, I have not considered it right to 

 reduce them to that group, or to attempt to fix their 

 natural relation to the two groups, particularly as a local 

 Fauna does not offer the best vehicle for changes in genera! 

 arrangement. 



