TIIK FRESH-WATER FISIIKS OF EUROPE. 



inches long 1 , but larger specimens are sometimes found; and in the Elbe and 

 II;i\vl it is known to reach a weight of five or six pounds (Fig. 205). 



The body is cylindrical, and more elongated than that of any other species 

 of the genus. The distance from the extremity of the sucking lip to the first 

 gill-arch is about one-ninth of the total length ; and the greatest height of the 

 forepart of the body is more than half this measurement. The relatively 

 small eye is only twice its diameter from the first gill-aperture. The eyes are 

 separated by five times the orbital diameter. The simple nasal aperture is a 

 long round opening, placed between the eyes ; it is surrounded with white 

 spots, and is the extremity of a blind tube, which does not penetrate the palate, 

 as in its marine ally, the Hag (Myxine glutinosa}. The mouth is built upon 



Fig. 205. PETROMYZON MAKINUS 



a great circular cartilage, which closely resembles the incomplete but similar 

 cartilage in the Tadpole, and shows no sign of division into two parts ; the 

 external margin of the mouth consists of a girdle of 

 short, slender, branched cirrhi, or little tentacles. 

 Within this band are the teeth, which are arranged 

 in rows. In the middle of the disc, behind the entrance 

 to the throat, is a curved plate, with seven to eight 

 strong sharp denticles (Fig. 206). Opposite this, in 

 front, are two teeth, sometimes stronger than the three 

 other lateral teeth on each side, which complete the 

 innermost circle. External to these are eight rows of 

 small denticles extending backward from the great" 

 mandibular tooth, which rows are nearly parallel to 

 each other, but diverge a little laterally. The rows of 

 teeth anterior to these are larger, six in number on 

 each side, and curved outward and backward, but the 

 two anterior rows on each side do not reach the central 



circle of teeth. On the tongue, which works backward and forward, there are 

 three strong denticulated horny teeth. All the teeth are hollow, and easily 

 fall off from the epithelium to which they are attached, but they are renewed, 



Fig 206. HEAD OF FETRO- 

 MYZOX MARIXVS, SEEN 

 PUOM BELOW. 



