THE NAUTILUS. 119 



which may be variable to a lesser or higher degree. It shows also that 

 it is impossible to found a species upon one or even a number of speci- 

 mens from one locality with any degree of certainty. 



4. Beaks of Galyculina. The presence of "calyculate" beaks 

 and of caps on them, has been regarded as characteristic, first, for the 

 type species ((7. lacustris Miill.), and then for the genus. Both these 

 characters had to be given up, as being not shown by all species 

 (e. g. transversa) of the otherwise well-defined genus. As to the 

 "caps," they are by uo means a constant feature of such species as G. 

 parfumeia, securis, etc., and during the last years numerous speci- 

 mens were seen with the beaks simply rounded and having not even 

 traces of caps. These caps are nothing else but the embryonic shell 

 of the mussel, which is oblong or elliptic in perpendicular section, and 

 the additional growth is formed at an angle as a rule. It seems that 

 the specimens without caps were hatched during the warmer season, 

 when the young may be expelled at an earlier stage of growth, while 

 in cold weather they are retained longer in the brood pouches of the 

 parent and there grow more convex. Numerous young have been seen 

 with several narrow stripes, separated by lines of growth, along the 

 edges of the valves. On the other hand, specimens of G. transuersa 

 are now and then seen with caps, and occasionally also Sphaeria and 

 different species of Pisidia. This point deserves to be studied more 



exactly. 



* * 



GENERAL NOTES. 



STATION OF LIMN/KA GRACILIS. We have received from Mr. 

 Bryant Walker the following note on the above species, extracted 

 from a letter from Dr. R. J. Kirkland : 



" Perhaps you will be interested in an observation respecting 

 Limnwa yracilis Say. I think Dr. DeCamp was the only person 

 who found it in Reed Lake, near this city (Detroit, Mich.), and 

 he only found it one year in May. He once told me he collected 

 eighty-five on the rushes, where 'they had come to spawn.' I have 

 searched for it in the spring for the past three years, but have never 

 found one. Last fall, as I wrote you, I found quite a number in 

 November. This fall, I found five on September 17, in the same 

 place as last fall. A week later found eighteen, two weeks later 

 found fifty. After that only two or three on each of several visits. I 

 think it was because the community was exhausted. Have searched 

 at other points in the lake, but unsuccessfully. They were found 



