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AMERICAN JOURNAL 



of omation, from that of the more common Eastern variety to 

 the almost entire absence of brown patches. These diversified 

 shells, it may be claimed, are distinct from dlternata. But au- 

 thorities will not be unanimous in according their assent to that 

 proposition. On the contrary they will be more generally re- 

 garded as varieties of alternata. The departure of dlternata 

 from its usual habits elsewhere, in this instance, presents an an- 

 alogy by which we may identify B. Tryoni with B. liypnorum. 



It is usual for Unio ligamentinus, Lam., to exhibit a pure 

 white nacre. At Grand Rapids it is not unusual to find this 

 species departing from its habits in other regions — exhibiting 

 specimens the nacre of which is pink, or even red. No one will 

 presume to set these red nacred shells apart as a distinct species 

 from ligamentinus. Yet, the same local influences which modify 

 Helix alternata and Unio ligamentinus, may be presumed to affect 

 Bulinus hypnorum, producing that variety to which, without 

 apparent necessity, specific value has been attached. It may be 

 well to consider at this time whether it would not be expedient 

 to revive the name glabra (De Kay) for the smaller Eastern 

 variety, if we are to admit the necessity for erecting a new spe- 

 cies upon the shells of Grand Rapids. 



Since mere questions of size and color are afforded as an ex- 

 cuse for separating varieties as species — when all other consid- 

 erations are adverse — let me suggest that, in the progress of my 

 investigation of the character of local species, I have often 

 noticed the effects of local influences in greatly modifying these 

 outward characters of a species. I find in some molluscs not 

 only a variation in the size and color of the shell, but also in the 

 color of the soft parts. An instance suggests itself in a small 

 operculated shell found at Mohawk, in the Erie Canal and Mo- 

 hawk River. In the river this species (Bythinella obtusa, Lea, 

 of W. G. Binney,) attains an unusually large size ; the soft parts 

 filling the apicial whorls are visible through the shell, and are of 

 a well marked orange color. In the canal the size is less, and 

 the orange tints of the soft parts are usually replaced with gray 

 tints. At a glance the shells would not seem to be of the same 

 species. But a rigid investigation will show that they are of one 

 species. 



Melantho gibba, Currier. 



The shells upon which t'he above name has been bestowed 

 were also sent to me by Mr. McNeil, both dry specimens, and 

 specimens in alcohol with the soft parts and embryonic young 

 enclosed. Mr. McNeil informed me that specimens had been 

 sent to Mr. Anthony, who decided they were a "new species," 



