THE NAUTILUS. 



VOL. XIX. SEPTEMBER, 1905. No. 5. 



NOTES ON YOUNG UNIONIDJE. 



BY L. S. FRIERSON. 



Recently while searching for young Unionidse I was rewarded by 

 obtaining a dozen little fellows averaging a quarter of an inch long. 

 One of these, a magnificent little Lampsilis anodontoides Lea, less than 

 one-fourth of an inch in length, exhibiting the glochidial valves, was 

 provided with a byssus four or five inches long, thus confirming my 

 previous observations. Several specimens of L. gracilis Barnes, and 

 one of L. Isevissimus Lea, were also taken so provided. The byssus 

 of one of these was fully eight inches in length. Several L. texasensis 

 were also taken, as already recorded by me. Several very small 

 Anodonta imbecilis Say, were captured, but these did not seem to 

 have byssi. Some time after, I was rewarded in an hour's search, 

 by a single specimen of Unio tetralasmus Say, perfect in every re- 

 spect, and only ^ of an inch in length. It was a jewel, but no sign of 

 its being provided with a byssus could be detected. 



Thus these preliminary and very scanty observations seem to limit 

 the possession of a byssus to Lampsilis (including in this term the 

 allied genus Medionidus). 



The byssi of these specimens came out of a narrow slit in the cen- 

 tral ridge of the foot, and located about the anterior third of the shell, 

 and all were firmly enough attached to support the weight of the 

 shell in the air, and of course amply strong to suspend the shell 

 while partially supported by the water. 



These baby shells revealed some facts about the so-called beak- 



