Miscellanies. 173 
species of Symphynota; and his last memoir contains descriptions 
_ and figures of four new species of Melania: viz. elongata, subularis, 
tuberculata and acuta; of one species of Helix, which he calls Caro- 
liniensis ; of two species of Carocolla: viz. helicotdes and spinosa, and 
of one species of Valvata, named by him, arenifera. He proposes 
also, the Fusus fluvialis of Say as anew genus; for the reason that 
the Canalifera are universally pelagian shells, while this is a fluviatile 
species, and therefore falls within the Melaniana. He calls it the Jo 
Susiformis,—accompanying his description of it with figures. 
With respect to Mr. Lea’s distribution of the Naiades into the two 
genera Unio and Symphynota,—the distinctive character for the 
former being valves free, and for the latter, valves connate,—it appears 
to us a real improvement, and one for which he deserves the thanks 
of all conchologists; since it banishes several genera, and provides 
in a natural and convenient manner for the disposition of the whole 
family. Certain it is, that the diagnosis of the old genera Anodonta, 
Iridina, Alasmodonta, Hyria and Dipsas was too difficult, if not in 
many instances wholly impracticable. We shall quote Mr. Lea’s 
observations upon the insufficiency of the teeth to furnish among the 
Naiades the grounds of division into genera. 
‘“‘The hinges in the species of the different genera glide or shade 
away so completely into each other, that I have no hesitation in say- 
ing itis entirely impossible for any naturalist to mark out a line of 
unvarying character to most of them.’ 
“If we examine the Anodonta cygnea, (Lam.) we find the margin 
under the beak and ligament to be an uninterrupted line. In the Iri- 
dina nilotica, (Sowerby) this line is slightly interrupted under the 
point of the beak. Inthe Anodon areolatus, (Swainson) we have 
this interruption more distinctly marked, the elevations being larger 
e curved, evidently forming an incipient tooth, which ap- 
proaches very closely to the Al dont: ‘ginata, (Say,) and forms 
with it a natural link. The next in the chain appears to be the Alas- 
of the genus Unio. The well known Unio pictorum (Mya pictorum, 
Lin.) presents us with cardinal and lateral teeth completely formed. 
In this genus, the Unio, we have an infinite variety in the forms of the 
teeth. In the Symphynota alata, (Nob.) the cardinal and lateral teeth 
