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310 MEMOIRS OF THE CARNEGIE MUSEUM 
Of the hermaphroditic nature of Symphynota viridis I feel more confident. 
I received thirty-four specimens of this species, collected by Dr. Atkinson on July 
11, 1908, and preserved the soft parts of fifteen of them. None was gravid, but 
they all had the female gills. In August, 1908, April, August, and September, 1909, 
I found this species repeatedly, altogether from fifty to sixty individuals, but all 
proved to be gravid, unless they were very young, and even in a number of the 
latter (in the second and third year of age) the female gill-structure was recog- 
nizable. In August, 1910, I collected altogether over one hundred specimens, and 
examined them in the field one by one, and every one had the female gill-structure. 
Thus in this case also I hunted in vain for males. 
It would be a very strange coincidence, that I should fail to find males only 
in these two closely allied species, if they exist. In all other species of Unionide 
I never had any trouble in discovering males, provided there were more at hand 
than a few. In fact, it seems that the males generally slightly outnumber the 
females. Nevertheless I could not find them in the above cases, and even those 
sterile specimens, which I took home as males, turned out to have the female 
structure. 
I therefore think that the conclusion is justified, that in these two species of 
Symphynota no males exist; and that they are, as a rule, hermaphrodites; although 
occasionally males may turn up, as is shown by the specimen from Cedar 
Point. 
I should also add that the Carnegie Museum possesses from a branch of the 
Rio Grande at Mercedes, Hidalgo County, Texas, an Anodonta, belonging to the 
imbecillis-group, which probably is A. henryana Lea. There are seven specimens, 
and all were collected by Dr. Atkinson on May 15, 1907, and every one of them is 
gravid. Of course, the number is too small to express a final opinion, yet, according 
to my experience with other species, even among seven individuals we should 
expect to find both sexes. Thus in this case also it is suggested, that we have to 
deal with a hermaphrodite, which is also probable on account of the affinity of 
this species with Anodonta imbecillis. 
I may possibly be able to give the results of further investigations of this 
question in the future. 
E. SX RECOGNITION IN THE YOUNG. 
Sterki (1898, p. 29) has pointed out, that in young individuals, from two to 
four years old, the sexual glands are not developed, and that in those of the Lamp- 
silis-type the sexual differences of the shells and the gills are not noticeable; there- 
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