15 



ventricle, but without the arterial bulb. The gills consist of 

 fixed sacs, six or seven on each side. Nasal aperture one, 

 situated on the head in front of the eves. 



Family Petromyzontidae. 



Lampreys. 



The body is eel-shaped, naked. The gills are seven on each 

 side ; the nostril does not open through to the palate ; the 

 mouth is placed somewhat inferiorly, and is adapted to suck- 

 ing, for it is in that way that the lampreys obtain their food, 

 using their numerous teeth to scrape and rasp the flesh off the 

 bodies of the unfortunate fish and other animals to whom they 

 may have attached themselves. The eyes, developed in the 

 adult, are rudimentary in the young ; the latter are larval with 

 a continuous vertical fin, an imperfect mouth and no teeth. 



Lampreys are called ' ' seven eyes ' ' from the seven gill 

 openings ; and "nine eyes" counting the gill openings, the 

 eye and the nostril, the last being counted in, once for each side. 



Petromyzon marinus L. 



Sea Lamprey. 



This species is found along the colder parts of both sides of 

 the Atlantic Ocean, ranging south to Virginia on our coast. It 

 is anadromous, ascending into small brooks to spawn, where it 

 builds so-called "nests" of stones and pebbles, within 

 which the spawn is deposited. It is supposed that after 

 spawning the adults die, as they disappear soon after. 1 



Lampreys are often found attached to sturgeons and salmons 

 as parasites. The mouth is full of teeth, which here are 

 horny excrescences resting on soft papillae. They are in 

 bands or laminae around the mouth and have several cusps. 

 The teeth situated further out (lateral) are bicuspid in the first 

 row, the others simple. The anterior lingual tooth has a deep 

 median groove. The dorsal fin is divided into two parts ; the 

 rear part merges into the caudal fin. The color of large speci- 

 mens is dark brown, mottled usually with blackish. They grow 

 to a length of three feet. 



1 Thoreau. A week on the Concord and Merrimack Rivers. A. Du- 

 meril. Les Poissons voyageurs, anadromes et catadromes. 



