lo University of Michigan 



the body, and vibrate feeljl\'. I'lit in siicli cases no emission of 

 eggs or milt is discerniljle. In the confmed space where spawn- 

 ing itsually occurs there wotild seem to be no room for the en- 

 wrapping of the female by the male, and it is doubtful if it 

 occurs with any regularity. Spawning seldom takes place 

 when the water is below iS^C, and is most vigorous at 20 to 



22 = C. 



Affinities of the Species: Since adults have been taken only 

 in the spawning season and are not found attached to fish, and 

 since our sections shoAV that the alimentary canal of the adult 

 is degenerated, there seems to be no ground to doubt that all 

 adults die soon after spav.ning. /. fossor is then analogous 

 to Bntospliciins zvilderi in which the adult j)arasitic life has 

 been lost. Tt is interesting to note that in both species the non- 

 parasitic condition is associated with a size small for the group 

 and with life in small bodies of water. IchtJiyouiyzon fossor 

 thus bears the same relation to members of its genus that En- 

 tosflioius Ti'/'Wrrz bears to its congeners, E. tridcntatus. E. 

 spadiceiis, etc. 



This species may be readily .separated from other North 

 American Ichthyomy/ons by the following characters : 



Icl'jliyoiiiysoii fossor Other species of Ichthyomyzon 



Maximum length al)out 150 mm. Maximum len.<>th al>out ^ck) mm. 

 Larvae at transforuiation equal in Larvae at transformation muclr 



length to maximum adults. smaller than maximum adults. 



Buccal funnel small. Buccal funnel large. (In an im- 



mature /. couc<-<lor it is ahout 

 twice as large as in a mature 

 /. fossor of the same length.) 

 Disc teetli small and l)Iunt — some Disc tcetli large and sharp, 

 even obsolete. 



Supraoral lamina with two small, Suprac-iral lamina with two or 

 Idunt, well separated cusps. more large, sharp;' closely ap- 



pressed cusps. 



