239 



CARTILAGINOUS FISHES. 



FROM the peculiar structure of the skeleton, these form an 

 interesting group, holding a place between the Cuttle-fish, in 

 which there is hut the rudiment of a skeleton, and the osseous 

 fishes, in which the vertehrated structure in this class of ani- 

 mals reaches its full development. Among them there is 

 great diversity. One little fish, of rare occurence, the 

 Lancelet (Ampliioxus lanceolatus), which is not much more 

 than an inch in length, has no skeleton, properly so called, 

 hut merely a membraneous thread ; in the Lamprey the 

 divisions of the vertebrae are marked, so that they resemble 

 beads placed on a string; in the Shark and the Sturgeon, 

 the divisions of the vertebra} are complete. 



PETROMYZHLE.* The family of the Lampreys (Fig. 194) 



Fig. 194. RIVER LAMPREY. 



comprises the Lancelot, the fish just mentioned. Some of 

 them dredged up in deep water, off the southern coasts of 

 England, by Mr. Mac Andrew, were exhibited by Professor 

 Edward Forbes, at the Southampton meeting of the British 

 Association, September, 1846. They have, ere now, been 

 ranked with the Mollusca, and exhibit peculiarities of a nature 

 so remarkable as to be objects of the highest interest to the 



* That is, the family of the " Stone-suckers," an appellation bestowed 

 on them because, by means of their circular mouths, they can adhere to 

 stones. Like other terms, it is derived from two Greek words. 



