Perhaps allied to the _Plagyodontidæ_ is also the large family of _Enchodontidæ_, widely represented in the Cretaceous rocks of Syria, Europe, and Kansas. The body in this group is elongate, the teeth very strong, and the dorsal fin short. _Enchodus lewesiensis_ is found in Mount Lebanon, _Halec sternbergi_ in the German Cretaceous, and many species of _Enchodus_ in Kansas; _Cimolichthys dirus_ in North Dakota. Remotely allied to these groups is the extinct family of _Dercetidæ_ from the Cretaceous of Germany and Syria. These are elongate fishes, the scales small or wanting, but with two or more series of bony scutes along the flanks. In _Dercetis scutatus_ the scutes are large and the dorsal fin is very long. Other genera are _Leptotrachelus_ and _Pelargorhynchus_. Dr. Boulenger places the _Dercetidæ_ in the order _Heteromi_. This is an expression of the fact that their relations are still unknown. Probably related to the _Dercetidæ_ is the American family of _Stratodontidæ_ with its two genera, _Stradodus_ and _Empo_ from the Cretaceous (Niobrara) deposits of Kansas. _Empo nepaholica_ is one of the best-known species. [Illustration: FIG. 98.—_Eurypholis freyeri_ Heckel. Family _Enchodontidæ_. Cretaceous. (After Heckel; the restoration of the jaws incorrect.) ] [Illustration: FIG. 99.—_Argyropelecus olfersi_ Cuvier. Gulf Stream. ] =The Sternoptychidæ.=—The _Sternoptychidæ_ differ materially from all these forms in the short, compressed, deep body and distorted form. The teeth are small, the body bright silvery, with luminous spots. The species live in the deep seas, rising in dark or stormy weather. _Sternoptyx diaphana_ is found in almost all seas, and species of _Argyropelecus_ are almost as widely distributed. After the earthquakes in 1896, which engulfed the fishing villages of Rikuzen, in northern Japan, numerous specimens of this species were found dead, floating on the water, by the steamer _Albatross_. The _Idiacanthidæ_ are small deep-sea fishes, eel-shaped and without pectorals, related to the _Iniomi_. =Order Lyopomi.=—Other deep-sea fishes constitute the order or suborder _Lyopomi_ (λυός, loose; πῶμα, opercle). These are elongate fishes having no mesocoracoid, and the preopercle rudimentary and connected only with the lower jaw, the large subopercle usurping its place. The group, which is perhaps to be regarded as a degenerate type of _Isospondyli_, contains the single family of _Halosauridæ_, 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. [Illustration: FIG. 100.—_Aldrovandia gracilis_ (Goode & Bean). Guadaloupe Island, West Indies. Family _Halosauridæ_. ]