254 
HISTORY OF BRITISH CRUSTACEA. 
body, are confused together, the thorax is very wide, and 
the eyes cease to be visible. 
Pam. IONIDM . 
Abdominal appendages filiform and surrounding the ab- 
domen. 
Gen. 133. XONE. 
Body, in the female, pyriform and very flat, in the male, 
narrow and elongated ; the abdomen of six segments, each 
bearing a pair of membranous, cylindrical, slender, very 
long appendages; in the female the appendages, fixed to the 
five first segments, are very long and arborescent. The head 
of the male has two pairs of antennae. 
Ione thoracica, Montagu, sp. (Plate XIV. fig. 8.) — 
Colour generally orange, appendages whitish ; male much 
more slender, and without cirri on front of the body. 
Colonel Montagu remarks, “This curious species inhabits 
the thoracic plate of Callianassa subterranea , concealing 
itself between the fleshy part and the shell, and forming a 
tumour on one side. Prom this situation I have extracted 
it alive, and have kept it in that state for several days in a 
glass of sea-water.” In the few specimens observed by 
