CHONDROPTERYGII. 657 



The same takes place with the lampreys and ammoccetes. 

 When the eggs are about to be protruded, they are de- 

 tached from the bunch already spoken of, and fall in all 

 probability into the cavity of the peritoneum, which com- 

 municates with the cloaca by two orifices, situate on the 

 edge of the rectum, nearly as in the rays. It is observable, 

 that the ovary terminates at a certain distance from the anus, 

 and that it is sufficiently fixed, so as not to approach the 

 conduits which make a communication between the cavity 

 of the peritoneum and the water in which the animal lives. 



The first genus, Petromyzon, distinguished from myxine 

 by the situation and number of the gill orifices, contains the 

 P. marinus, Great or Sea lamprey, an inhabitant of the sea, 

 and occasional visitant, in the breeding season, of rivers and 

 streams. It attaches itself, by means of its sucker mouth, 

 with great force to rocks and stones, from whence its name 

 lamprey, (a lambendo petris) which the rage for nomen- 

 clature must needlessly alter to Cyclostoma, implying the 

 circular form of its mouth. This mouth, singular in its con- 

 struction, is armed with regular rows of conical bent 

 teeth, set round a common centre, the largest of them 

 being nearest to the throat. These teeth are covered with 

 a solid horny matter, of an orange colour, which is detach- 

 able by maceration and ebullition. Our figure of this curious 

 mouth will convey a better idea of it than a laboured verbal 

 description; but it is necessary to add that the opening 

 of the throat is in the centre of the large disk of the mouth, 

 and the membrane which forms there the commencement of 

 the oesophagus is soft and mucous. In the lower part, where 

 the tongue is usually situated, there is a mass of teeth of 

 the same colour as the outer rows, but supported by moveable 

 cartilages acting like hyoid bones ; the whole has some simi- 

 larity to the top of the larynx in man. Although these little 

 teeth are numerous, they are connected only to three principal 



vol. x. u u 



