PISCES. 99 



the anterior part of the cranium ; small branchial ribs appa- 

 rent. 



GENUS II. PRISTIS, Lath. Saw-Fish. 



Uniting with the form of the Shark a body flattened before ; 

 branchiae opening below as in Raid, and a very long snout or 

 depressed beak, like the blade of a sword, armed on each side 

 with strong, bony, trenchant and pointed spines ; this weapon 

 enables them to attack the largest Cetacea. 



GENUS III. RAIA, Lin. Ray. 



Body flattened horizontally, and resembling a disk on ac- 

 count of its union with the exceedingly broad and fleshy 

 pectorals joined with each other to the snout, or before it, and 

 which extend behind the two sides of the abdomen to near 

 the base of the ventrals ; eyes on the dorsal surface as well 

 as vents (two openings which communicate with the bran- 

 chial cavity and supply it with water, when the gullet of the 

 animal is filled with prey) ; mouth, nostrils and branchial 

 orifices on the ventral surface; dorsals almost always on the 

 tail. 



ORDER III. SUCTORII. 



Mouth in a ring ; skeleton more imperfect than in any 

 other vertebrated animal ; neither pectorals nor ventrals ; body 

 elongated and terminated before by a fleshy lip, circular or 

 semicircular, sustained by a cartilaginous ring, arising from 

 the soldering of the palatines to the under jaw ; the branchiae, 

 instead of combs, present the appearance of purses, formed by 

 the union of one face of a branchia with the opposite one of 

 its neighbour. One remarkable genus. 



GENUS PETROMYZON, Burner. Lamprey. 



Seven branchial openings on each side; skin of the tail, 

 above and beneath, turned up into a longitudinal crest, which 

 supplies the place of a fin, but in which the rays are hardly 

 distinguishable fibres ; two dorsals, the posterior one joining 

 the caudal ; maxillary ring armed with very strong teeth ; 





