8 University of Michigan 



six inches in diamcte-r. and in Vv'aler irovA eight to eighteen 

 inclies deep. The stream at this point is not more than thirty 

 feet wide, with a strong current. Adults have been seen or 

 collected only during the spawning season. 



They are rarely seen to sv im free even for a few feet, but 

 are often found j)rogressing or wriggling between stones. They 

 are usually so hidden among or beneath stones of three to six 

 inches diameter that only the tip of the tail is visible. The 

 animals take possession of chinks beneath such stones as may 

 be lodged loosely, and extend the natural cavities by removing 

 sand and gravel. In enlarging the cavity the lamprey attaches 

 itself by the mouth to ])ebbles, and tosses them up and out 

 from between the larger stones. Active lashing of the body 

 at the same time serves to stir up the sand, which is swept 

 away by the current. On rare occasions an individual may 

 attempt to remove a larger stone by attaching himself to it. 

 loosening the stone l.»y wriggling the bod_\ and then allowing 

 the current to carry himself and burden downstream — as is 

 the common habit in Ujitosphcniis z^.'ildcii. Like the brook 

 lamprey, this species has the habit of attaching the mouth to 

 large stones and throwing the body into vigorotis vil)rations. 

 However, the haljit differs from th.at of the l)rook lamprey in 

 that the axis of the body is often nearly vertical, and what- 

 ever inclination there may be toward the horizontal is quite as 

 likely to be upstream as downstream. The vibrations occur 

 when the animal is partially hidden among stones as well as 

 when it is in the oj)en. The J)rook lamprey lies with th.e body 

 nearly horizontal and with the head directed upstream during 

 these vibrations. \\'hen ])laced in a bacteria di.sh in bright 

 light the animal becomes restless and moves continually until 

 the dish is covered. Although not so sensitive to current as 

 the Ijrook lamprey, fclitlioniy.con fossor does exhibit a tendency 



