Class MARSIPOBRANCHII. 



Order HYPEROARTIA. 



Family PETROMYZONTID^, (the Lampreys.) 

 Genus AMMOCCETES, Dunieril. 



175. Ammocoetes niger (Eaf.) Jor. Small Black Lamprey. (M. V. 

 349 ; Petromyzon niger Nelson 52.) 



Common in small streams in many places, ascending to spawn 

 in the spring. Pecatonica R., Freeport. 



176. Ammocoetes argenteus (Kirt.) Jor. Silvery Lamprey. (M. V. 

 349; Iclithyomyzon argenteus Nelson 52.) 



Probably more or less abundant through the state. 111. R., 

 Pekin. 



177. Ammocoetes hirudo (Grrd.) Jor. Leech Lamprey. (M. V. 350 ; 

 Ichtliyomyzon Mrudo Nelson 52.) 



A species supposed to be the one to which Girard gave the 

 name of Mrudo is quite abundant in the Mississippi and lower 

 Ohio. *Ohio R., at Cairo. 



* Where exact localities are given in the preceding paper, they are in nearly 

 every case taken from specimens now in the Laboratory, collected by myself or my 

 assistants. S. A. F. 



