Occasional Papers of the Mnscuui of Zoology 5 



Description of Lari'a : Eight larvae have heen examined 

 (Cat. Xos. 48384-48391, ^Museum of Zoology, University of 

 2*klichigan ), six from Mill Creek and two from the Huron 

 River near Ann Arhor. The following description is based on 

 specimen number -]8386 taken in Mill Creek, Washtenaw Coun- 

 ty, Michigan, May 21. 1916. 



With the usual ammocoetes facies. Length, 135 mm.; tip- 

 of snout to vent, 70.37 ; ti]) of snout to anterior margin of dor- 

 sal, 50.37; last gill opening to vent, 51.85; last gill opening to 

 anterior margin of dorsal, 31.85; tip of snout to last gill open- 

 ing, 18.52; ti[) of snout to first gill opening, 8.15; width imme- 

 diately behind branchial l)asket, 5.19; depth immediately be- 

 hind l)ranchial basket, 6.67. Muscular impressions between 

 last gill opening and vent. 51. Shape of mouth and form of 

 oral villi as in Bntosphcnus 7cihieri. Dorsal fin { I'l. 1, fig. 4) 

 continuous, not separated into anterior and posterior dorsals, 

 increasing graduall} in height posteriorly to reach its maximum 

 height behind the vent ; height in its anterior portion, .56. 

 Posterior portion slightly convex in outline ; greatest height. 

 1.48; continuous with caudal, the junction indicated by a shal- 

 low notch. Xo anal fin. 



The lar\al characters seem to be more constant than those of 

 adults. There are, however, slight variations in proportions 

 as mav be seen in the following table : 



