=Chirothricidæ.=—The remarkable extinct family of _Chirothricidæ_ may be related to the _Synodontidæ_, or _Myctophidæ_. In this group the teeth are feeble, the paired fins much enlarged, and the ventrals are well forward. The dorsal fin, inserted well forward, has stout basal bones. _Chirothrix libanicus_ of the Cretaceous of Mt. Lebanon is remarkable for its excessively large ventral fins. _Telepholis_ is a related genus. _Exocœtoides_ with rounded caudal fin is probably the type of a distinct family, _Exocœtoididæ_, the caudal fin being strongly forked in _Chirothrix_. The small extinct group of _Rhinellidæ_ is usually placed near the _Myctophidæ_. They are distinguished by the very long gar-like jaws; whether they possessed adipose fins or luminous spots cannot be determined. _Rhinellus furcatus_ and other species occur in the Cretaceous of Europe and Asia. Fossil forms more or less distinctly related to the _Myctophidæ_ are numerous. _Osmeroides monasterii_ (wrongly called _Sardinioides_), from the German Cretaceous, seems allied to _Myctophum_, although, of course, luminous spots leave no trace among fossils. _Acrognathus boops_ is remarkable for the large size of the eyes. [Illustration: FIG. 95.—_Rhinellus furcatus_ Agassiz. Upper Cretaceous of Mt. Lebanon. (After Woodward.) ] =Maurolicidæ.=—The _Maurolicidæ_ are similar in form and habit, but scaleless, and with luminous spots more highly specialized. _Maurolicus pennanti_, the "Sleppy Argentine," is occasionally taken on either side of the Atlantic. Other genera are _Zalarges_, _Vinciguerria_, and _Valenciennellus_. =The Lancet-fishes.=—The _Plagyodontidæ_ (_Alepisauridæ_) contains the lancet-fishes, large, swift, scaleless fishes of the ocean depths with very high dorsal fin, and the mouth filled with knife-like teeth. These large fish are occasionally cast up by storms or are driven to the shores by the torments of a parasite, _Tetrarhynchus_, found imbedded in the flesh. It is probable that they are sometimes killed by being forced above their level by fishes which they have swallowed. In such cases they are destroyed through the reduction of pressure.