THE NAUTILUS. 7 



cidental iDfections upon an inappropriate host. The great 

 majority of infections were by a glochidium unknown to me. 

 They were deeply imbedded in the external gills of the Necturus 

 and by keeping the animals alive all winter I succeeded in car- 

 rying the young mussels through to the juvenile stage, these 

 being shed the last week in May, soon after which 1 obtained 

 the young mussels. The parasitic period is a long one from the 

 date the infected salamanders were captured, October 17th to 

 the last of May, being over 7 months. By this test the appro- 

 priateness of the host was satisfactorily demonstrated. 



These glochidia were different from any in our station collec- 

 tion of which we supposedly had a complete faunal set with 

 one or two exceptions which I knew did not answer the case in 

 question, I looked up all the known Najades which might 

 have a range to the Mississippi River in Eastern Iowa and found 

 that one species was given which we did not have. This was 

 Hemilastena ambigua, Say or Unio hildrethianus, Lea. An in- 

 quiry at the Academy of Sciences, Davenport, la., disclosed 

 the fact that there was one record of collection for Davenport.* 



Lea^ figures the glochidium of this species but it is so small 

 and so like that of other species that without dimensions a cer- 

 tain identification could not be made from it. As the likeli- 

 hood of finding material in some collection seemed slight I de- 

 cided to look for gravid mussels and make a direct comparison. 

 From the literature and such information as could be gathered 

 from experienced collectors, this rare species has the peculiar 

 habit of living under flat stones. This seemed to present a 

 difficulty in collection, for the water was deep at the point where 

 the Necturus had been taken. I had dredged here considerably 

 but no example of this species were in the hauls. Their habitat 

 would seem to account for this failure to secure them as an or- 

 dinary boat dredge would be likely to miss them protected as 

 they are by the stone above. The best chance for success 

 seemed to be to locate them in some small stream. In Mr. F. 



" I am indebted to the Davenport Academy of Sciences for their assistance 

 in this matter and especially to Mr. Paarmann and Miss S. F. Sheldon who 

 kindly looked up the specimen and records. 



* Lea, Isaac, Observations on the Genus Unio, vol. vi, p. 49, pi. 6, fig. 31. 



