FISHES. 95 



i;7*. Ksox. Head somewhat flattened above : moitt h wide: 

 tongue broad, loose: teeth sharp, in the jaws, palate, 

 and tongue : nostrils double, near the eyes : gill- 

 membrane 7-12-rayed : body lengthened, compressed : 

 lateral-line straight, nearer the back, hardly visible : 

 dorsal and anal fins short, and mostly opposite. 



28. ARGENTINA. Teeth in the jaws and on the tongue 

 gill-membrane 8-rayed : vent near the tail : ventral-Jinn 

 many rayed. 



29. ATHERINA. Upper-jaw a little flattened: gill-mem- 

 brane 6-rayed: body marked on the sides with a silvery 

 stripe. 



SO. MUG ii-. Lips membranaceous, the lower-one cari- 

 nate within : teeth minute : mouth with an inflected 

 callosity at the corners : gill-membrane with 6 curved 

 rays ; the covers smooth and rounded : body fleshy, 

 with large scales : dorsal-fins two. 



31. EXOCCETUS. Head scaly: mouth without teeth ; the 

 jaws connected on each side : gill-membrane 10- rayed: 

 belly angular : pectoral-fins very large and Jong, giving 

 the power of flight. 



32. CLUPEA. Head compressed : mouth rough within: 

 upper-mandible with the side-plates serrate : gill- 

 membrane 8-rayed, the covers of 3 or 4 pieces ; gills 

 internally .setaceous : lateral-line near and parallel 

 with the back : belly sharp, and generally serrate : 

 ventral-fns about 9-rayed : tail forked. 



33. CYFRINUS. Mouth small, without teeth; teeth in 

 the throat; gill-membrane 3-rayed : ventral-fins mostly. 

 9-rayed. 



ORDER V. CARTILAGINEI. 



Fishes with a cartilaginous sceleton. 



34. PETROMYZON. Body eel-shaped : mouth placed un- 

 derneath, with numerous teeth in circular rows : 

 spiracles 7 on each side the neck, and one on the nape: 

 pectoral and ventrat-Jins none. 



35. GASTOBRANCHUS. Body eel-shaped : mouth placed 

 underneath, bearded with numerous pectinate teeth : 

 spiracles 2, beneath the belly. 



36. RAJA. Mouth placed underneath, transverse, armed 

 with teeth: spiracles 5 each side, placed obliquely and 

 beneath near the neck : body thin, flat, more or less 

 rhombic. 



37. SQUALUS. Mouth placed underneath the anterior 

 part of the head, armed with numerous teeth disposed 

 in rows : spiracles 4-7, semilunar, on the sides of the 

 neck : body oblong, more or less cylindrical. 



