30 A HISTORY OF RECENT 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 antennze and hind legs, can 
stretch over a space of three inches. In the Hyperidea, 
Rhabdosima armatum* 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 boast of the Gam- 
maridea is Hurythénes 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 centimétres 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 1885 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 Amphipoda yet known. 
The Entomostracans make their position in the world’s 
1 It is doubtful whether the change of this name to Xiphocephalus 
armatus, as proposed by Dr. Bovallius, can be justified, since the 
name Xyphicéphale was only given by Eydoux and Souleyet on Guérin’s 
authority in trivial not in scientific 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. 
