CHONDROPTERYGII BRANCHIIS FIXIS. 241 



branchial ones, which are hardly perceptible in the Squali and Rays, 

 are here greatly developed and united with each other, forming a 

 kind of cage, while there are no solid branchial arches. The bran- 

 chiae, instead of being pectinated as in all other fishes, resemble pur- 

 ses, resulting from the junction of one face of a branchia with the 

 opposing one of its neighbour. The labyrinth of the ear is en- 

 closed by the cranium, and the nostrils open externally by a single 

 orifice, in front of which is a blind cavity. 



Petkomyzon, Li n . ( 1 ) 

 Tlie Lampreys have seven branchial openings on each side; the skin of the 

 tail above and beneath is turned up into a longitudinal crest which supplies 

 the place of a fin, but in which the rays resemble scarcely visible fibres. 



The maxillary ring of the True Lamprey is armed with strong teeth, and 

 the interior disk of the lip, which is very circular, is furnished with tuber- 

 cles covered with an extremely hard shell, and similar to teeth. There are 

 two longitudinal rows of small teeth on the tongue, which moves backwards 

 and forwards like a piston; by this, that suction is produced which distin- 

 guishes this animal. Water reaches the branchiae from the mouth by a par- 

 ticular membranous canal, placed under the oesophagus and perforated with 

 holes, that may be compared to a trachea. These fishes habitually fix 

 themselves by suction to stones and other sohd bodies; they attack the 

 largest fishes in the same way, and are finally enabled to pierce and de- 

 vour them. 



P. marinus, L. (The Sea Lamprey.) Two or three feet in length, 

 marbled with brown on a yellowish ground; two large approximated teeth 

 on the upper part of the maxillary ring. It ascends the mouths of rivers in 

 the spring, and is highly esteemed. 



P . fluvialis, "L. (The River Lamprey.) From a foot to eighteen Inches 

 in length; silvery, blackish and oHve on the back; first dorsal very distinct 

 from the second; two large separated teeth on the upper part of the maxil- 

 lary ring. Inhabits rivers, &c. 



Myxine, Lin. 

 But a single tooth on the upper part of the maxillary ring, which is alto- 

 gether membranous; lateral dentations of the tongue strong, and arranged 

 in two rows on each side, so that the jaws of these fishes seem to be lateral 

 like those of Insects or the Nereides, which induced Linnaeus to place them 

 in the class of Vermes; the rest of their organization, however, is analogous 



(1) Lamproye, Lampreda, Lamprey, corruptions of Lampetra, which is 

 itself modern, and, according to some, derived from Lambendo, petras. 

 Petromyzon is the Greek translation of the same, by Artedi. 

 2 F 



