Stee as 
; 
F 
A 
= 
; 
: 
i 
k 
; 
1878. | Zoölogy. ` 473 
Barnes. Through the same medium other western species may 
be introduced. r 
Unio pressus*Lea, was also found by the writer, near the same 
locality (within three miles) in May, 1877, but under conditions 
that preclude the possibility of its introduction in a like manner. 
Two specimens were taken from a small lake near Herkimer, N. 
Y. The lake lies between high hills and receives a$ its water- 
supply an artificial branch of West Canada Creek, a mountain 
stream having no connection with the Erie canal, or any stream 
that could possibly reach it from the west or south. It empties into 
the Mohawk, but over a very rocky bed, and after a considerable 
fall. The species is essentially western, but is recorded at Troy, 
N. Y. (Vide Lewis in Bulletin Buf, Soc. Nat. Sci: Aug. 1874, p 
127). Its occurrence in the latter locality may be explained, 
perhaps, in a manner similar to the preceding, though at no known 
intermediate localities has it been found. The problem to be 
solved is: How came this western species in this isolated eastern 
lake? Mr. Darwin, (in “ Origin of Species,” p. 344, Ed. 1877) has 
conjectured a probable mode of distribution, relating particularly 
' to certain fresh-water univalves. hat Mr. Darwin conjectured 
sion, to which is attached a bivalve shell, the former caught and 
firmly held by the latter. pee 
The young of Uniones, since they are capable of swimming 
freely about, may be distributed in the manner suggested by Mr. 
Darwin; viz: attaching themselves to pond-weeds, the latter 
being often carried away by water-fowl. That Lznnaee and* 
Planorbis do thus attach themselves every collector knows. What- 
ever the manner or cause of its introduction Unio pressus is found 
in the above lake, absolutely foreign to any stream through which 
the species might have been introduced, This species, as well as 
the preceding, may yet become colonized in the Mohawk River. 
The fact of its occurrence now and its probable recent introduc- 
tion in the locality mentioned, under conditions that seem physi- 
cally impossible, may be of interest when the geographical 
distribution of the Unionidae comes to be more fully studied.—A. 
Ellsworth Call. 4 
sr hE S 
that this water is the ordinary urine of the reptile, voided in this 
4 
