“0 ZOOLOGY: 
would lead me to adopt the name given by that author, did it not appear 
that the work was not published for several years after it was printed. 
It was not known to the naturalists of this country, France, Germany, or 
England, until the year 1824.” (Say’s Am. Conchology.) Swainson uses 
both names, restricting Schumacher’s to the Margaritifera (pl. 76, jig. 47) 
of Europe, and Say’s to the form A. undulata. 
Strophilus, Rafinesque, 1820 (Pseudodon, Gould, 1844, Proceed. Bost. 
Soe. p. 160, with four species), has a small swelling instead of regular 
cardinal teeth, and the soft parts differ in having the young, after they leave 
the ovaries, deposited transversely in the exterior branchiz, instead of being 
in vertical folds, as in most of the species. In Diplasma of the same’ 
author, founded on some shells from Hindostan, there are anterior as well 
as posterior lamellar teeth, and these are double in the right valve anteriorly, 
and in the left posteriorly. 
Rafinesque, in the “Continuation” of his Monograph of the Bivalve 
Shells of the river Ohio, institutes a genus, Loncosilla, for a solenoid shell, 
brought by Dr. Burrough from the river Jellinghy, in Bengal. Rafinesque 
considered it to be allied to Anodonta, on account of its fluviatile habits, 
but the characters of the shell are such as to induce us to coincide with 
Dr. Burrough in believing it to be essentially a solen. The shell is less 
than an inch long, ‘somewhat swelled, both ends rounded, and a little 
gaping, back horizontal; outside and inside smooth and whitish.” 
Lamarck considered these mollusca to be hermaphrodite; and the 
dissections of competent anatomists, such as Neuwyler and Van Beneden, 
confirm this view. 
Dr. J. P. Kirtland of Cleveland, well known as a successful cultivator of 
natural science, announced, in the twenty-sixth volume of Silliman’s 
Journal, his ability to distinguish the sexes by the shell alone in this sub- 
family. It is well known that the shells of many (although not all) species 
present individuals which are more full at the base posteriorly, and these 
were assumed to be females, the enlargement of the shell being, as it was 
thought, required for the gravid branchiz. Some species, as Unio viridis, 
may be gravid without exhibiting any change of external form. If some 
individuals remain barren, and others prolific through a course of years, 
it is possible that the weight of the gravid branchiz may cause the soft 
_ parts to descend and bring with them the shell-secreting mantle, which may 
account for the enlargement without recourse to the theory of separate 
sexes, which are not found in the allied families. But this explanation will 
hardly account for the second. form in Unio velum or U. flexuosus, or for 
the extraordinary transverse diameter (as in Unio siliquoideus) which is 
sometimes assumed in addition to the more common posterior enlargement. 
Dr. Kirtland has discovered the presence of a line which he compares to 
a byssus (Silliman’s Jour., 1840, vol. xxxix. p. 166), by which the young of 
various species of Unio attach themselves to extraneous objects, a character 
which indicates an affinity with the Arcidx and Mytilidse, with which they 
have other affinities. 
The genus Castalia, from the rivers of South America, is allied to Arca 
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