470 PETROMYZID/E. 



eyes, and gill-covers ; while the fish under consideration has 

 neither eyes nor gill-covers, nor any fins except one along 

 the back. 



Supported by the opinions of three or four zoological 

 friends, I have placed this little animal in this family, near 

 the cyclostomous fishes, believing it to be, as far as at present 

 known, the lowest in organization among this class ; and 

 although I am unwilling to mutilate entirely by my rough 

 dissection the only specimen probably I shall ever possess, 

 and which is perhaps unique, I shall yet be able to show, by 

 the figures given and some further description, that this 

 animal is entitled to a place at the end of the present 

 family. 



The form of the fish is compressed ; the head pointed, 

 without any trace of eyes ; the nose rather produced : the 

 mouth on the under edge, in shape an elongated fissure, 

 the sides of which are flexible ; from the inner margin ex- 

 tend various slender filaments, regularly disposed, which 

 cross and intermingle with those of the opposite side. Along 

 the sides , of the body the muscles are arranged in regular 

 order, diverging from a central line, one series passing ob- 

 liquely upward and backward, the other series as obliquely 

 downward and backward : the anal aperture is situated one- 

 fourth of the whole length of the fish, in advance of the 

 end of the tail ; the tail itself pointed : from the nose to 

 the end of the tail a delicate membranous dorsal fin extends 

 the whole length of the back, supported by very numerous 

 and minute soft rays ; the surface of the body smooth. 



The body is strengthened and supported internally 

 throughout its length by a flexible cartilaginous column, 

 from which the numerous muscles diverge ; the cavity of the 

 abdomen is comparatively large ; the intestine a canal of 



