i 34 The Grayling and the Smelt 



enlarged, and the ventrals are well forward. The dorsal fin, 

 inserted well forward, has stout basal bones. Chirothrix libani- 

 cus of the Cretaceous of Mt. Lebanon is remarkable for its exces- 

 sively large ventral fins. Telepholis is a related genus. Exo- 

 ccetoides with rounded caudal fin is probably the type of a 

 distinct family, Exoc&toididce, the caudal fin being strongly 

 forked in Chirothrix. The small extinct group of Ekinellidaz is 

 usually placed near the Myctophida. They are distinguished 

 by the very long gar-like jaws ; whether they possessed adipose 

 fins or luminous spots cannot be determined. Rhinellus fur- 

 catus and other species occur in the Cretaceous of Europe and 

 Asia. Fossil forms more or less distinctly related to the Mycto- 



FIG. 95. Rhinellus furcalus Agassiz. Upper Cretaceous of Mt. Lebanon. 



(After Woodward.) 



phidce 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. 



Maurolicidae. The Maurolicida 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 Plagyodontida (Alepisauridce) con- 

 tains 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. 



Every part of the body is so fragile that perfect specimens 

 are rare. The dorsal fin is readily torn, the bones are very 



