FISHES. 83 



27. Esox. Head somewhat flattened above: mouth 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-jins 

 many rayed. 



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

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

 stripe. 



30. Mugil. 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 long, giving 

 the power of flight. 



32. Ceupea. 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-fins about 9-rayed : tail forked. 



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

 the throat; gill-membrane 3- rayed : ventral-jins mostly 

 9-rayed. 



ORDER V. CARTILAGINEJ. 

 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-fins 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. SQUALtJS. Mouth placed underneath the anterior 

 part of the head, armed with numerous teeth disposed 

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

 neck : body oblongs more or less cylindrical* 



