THE NAUTILUS. 15 



is near the limit of the range of this species, and tlie latter does not 

 go much farther up stream. All of the species are rather small, 

 which is most striking in Lampsilis recta, which actually is repre- 

 sented by a dwarf race. 



All the species have been found alive, except Quadrula undulata. 



DuNKARD Creek (collections made on July 8 and 9, 1908). 



1. Lampsilis ventricosa (Barn.). 8. Slrophifus undulatus (Say). 



2. Lampsilis luteola (Lam.). 9. Anodonta grandis (Say). 



3. Lampsilis recta (Lam.j. 10. Symphynota costata (Rat.). 



4. Lampsilis iris (Lea). 11. Unio gibhosus (Barn.). 



5. Proptera alata (Say). 12. Quadrula riibiginosa (Lea). 



6. Tritogoniatuberculata(Ba.rn.'). 13. Quadrula tuberculata (VLaiS). 

 1 . Ptythobranchus phaseolus 



(Hildr.). 



Of these, only Lampsilis luteola and Anodonta grandis were found 

 alive : the condition of the creek was not favorable for collecting 

 (first and second day after a heavy thundershovver). It is probable, 

 that the fauna is not complete, and I cannot say anything about the 

 frequency of the single species. 



VARIATION. 

 BY REV. HENRY W. WINKLEY. 



First, nature never makes two individuals exactly alike ; 

 secondly environment. One hundred shells of the same species 

 from a given locality will show individuality. Compared with 

 a group of the same species from another region there is another 

 difference. Like the difference between races of the human 

 family, this is undoubtedly due to environment. At Eastport, 

 Maine, where the Bay of Fundy tides create strong currents, 

 chitons, limpets and other forms are in profusion and attain un- 

 usually large size. These ma}' be called sedentary forms and 

 depend on food being brought to them. A few feet away Bucci- 

 num is abundant but small. The same is true of Lunatia heros 

 found in neighboring waters. These are carnivorous forms and 

 are much larger at Casco Bay and its neighborhood. 



Haminea solitai'ia is a white shell. A small colony from the 



