138 The Grayling and the Smelt 
numerous specimens of this species were found dead, floating 
on the water, by the steamer Albatross. 
The Idiacanthide are small deep-sea fishes, eel-shaped and 
without pectorals, related to the Inzomz. 
Order Lyopomi.—Other deep-sea fishes constitute the order 
or suborder Lyopomi (Avos, loose; mapa, opercle). These are 
elongate fishes having no mesocoracoid, and the preopercle 
rudimentary and connected only with the lower jaw, the large 
Fic. 100.—Aldrovandia gracilis (Goode & Bean). Guadaloupe Island, West 
Indies. Family Halosauride. 
subopercle usurping its place. The group, which is perhaps to 
be regarded as a degenerate type of Isospondyli, contains the 
single family of Halosauride, with several species, black in 
‘color, soft in substance, with small teeth and long tapering 
tail, found in all seas. The principal genera are Halosaurus 
and Aldrovandia (Halosauropsis). Aldrovandia macrochira is 
the commonest species on our Atlantic coast. 
Several fossil Halosauride are described from the Creta- 
ceous of Europe and Syria, referred to the genera Echidnocephalus 
and Enchelurus. Boulenger refers the Lyopomi to the suborder 
Heteromi, 
