30 A HISTOHY OF EECENT CRUSTACEA 



there are Gammarids, Hyperids, and Caprellids, of micro- 

 scopic proportions, but for colossal species each Amphipod 

 division must be content to compare its members one with 

 another, rather than with the outside world. In the 

 threadlike Caprellidea, some of which might be regarded 

 as creatures of only one dimension, the Challenger species, 

 Dodecas elongata, by help of its antennae and hind legs, can 

 stretch over a space of three inches. In the Hyperidea, 

 Rhahdosoma armatam ^ is not quite so thin, but its length 

 is greater, since the tip of its rostrum is sometimes nearly 

 five inches distant from the extremity of its caudal appen- 

 dages. In the same section the remarkable genus Cystisoma 

 has species which combine a length of four or five inches 

 with the respectable breadth and depth of an inch in the 

 amplest part of the head. The chief boasfc of the Gam- 

 maridea is JEurijthenes gryllus (Lichtenstein in Mandt). 

 The first specimen observed of this full-bodied animal was 

 three inches long and two inches and a quarter round the 

 waist. It was disgorged in the far north by a wounded 

 arctic petrel. Twenty-seven years later it again attracted 

 scientific attention, singularly enough the specimen this 

 time coming from the far south, for it was taken from the 

 stomach of a fish caught off" Cape Horn. Its body was 

 nine centimetres long and three deep — in other words, more 

 than three and a half inches in length and more than one 

 inch in depth. In recent years the apparent anomaly of its 

 occurrence both in arctic and sub-antarctic waters has been 

 explained by evidence that it can make itself at home in the 

 intervening expanse, since in 1883 the American steamer 

 Albatross captured a specimen over four and a half inches 

 long, in deep water off the middle Atlantic coast of the 

 United States. This must be regarded as the bulkiest of 

 the Amphipod a yet known. 



The Entomostracans make their position in the world's 



* It is doubtful whether the change of this name to XipJioceplialus 

 armatus, as proposed by Dr. Bovallius, can be justified, since the 

 name XypMccphale was only given by Eydoux and Souleyet on Guerin's 

 authority in trivial not in scientitic form, an ill-spelt French name for 

 a genus rather hinted at than established or defined, the name more- 

 over not being definitely given but only contingently suggested. 



