AS NCOeDOON: 
Prare If. 
Species 2. (Fig. 2, 46, Mus. Sowerby ; vide Pl. 1.) 
ANODON CYGNEUS. 
In order to present a fair idea of the species, it is ne- 
cessary to give a figure of the more ordinary flattened 
form, just young enough to show the green rays. 

Species 3. (Mus. Sowerby.) 
ANODON LATO-MARGINATUS. dn. testdé solidd, oblique 
ovata, viridi, fasciis nigrescentibus teniatd, laevigata, 
anticé flecuosi, subhianti, intts nacred, vivide irides- 
centi, lamind cardinali subincrassatd, area ligamenti- 
Seré complanatd ; latere antico brevissimo, contracto, 
margine dorsali declivi ; latere postico oblique tumido, 
ad marginem ventralem expanso, termino elevato, viz 
acuminato, area dorsali subalatd, margine versus um- 
bones declivi. 
THE WIDE-BORDERED ANOoDON. Shell solid, obliquely 
ovate, green, banded with blackish stripes, smooth, 
flexuous in front, rather gaping, pearly within, and 
vividly iridescent, hinge lamina rather thickened, 
with a flattened ligamentiferous area; anterior side 
very short, contracted, dorsal margin sloping; pos- 
terior side obliquely tumid, expanded at the ventral 
margin, elevated at the end, scarcely acuminated, 
with subalate dorsal area, the margin sloping towards 
the umboes. 
Lea, Obs. Unio, i. p. 188. pl. xii. f. 34. 
Var. Anodon rotunda, Spix. 
Hab. Paraguay et Para, S. America. 
It is difficult to understand why the genus Leila 
should be separated from the other toothless Naiades ; 
but this species, although not admitted into that genus 
by those authors who adopt it, is evidently a shell of the 
same character as Leila Blainvilliana of the same authors. 
It has a thickened hinge-line, is very oblique, and slightly 
gaping. 
Species 4. (Mus. Sowerby. 
ANODON RosTRATUS. Aun. testd subtrigond, alata, oli- 

vaced, concentrice rugatd, tenui, intts vividé irides- 
centi; latere untico brevi, angusto, rotundatim acu- 
minato ; latere postico tumido, lato, obliqué expanso, 
obscuré biangulato, in rostrum breve trencatum pro- 
ducto, super angulum contracto, in alam elevatam 
expanso, margine dorsali versus umbones declivi, um- 
bonibus complanatis. 
THE BEAKED ANoDON. Shell subtrigonal, winged, 
olive, concentrically wrinkled, thin, brightly irides- 
cent within; anterior side short, narrow, roundly 
acuminated ; posterior side tumid, wide, obliquely 
expanded, obscurely biangular, produced into a 
short truncated beak contracted above the angle, 
expanded into an elevated wing, dorsal margin 
sloping towards the umboes, umboes flattened. 
RokteL, Jay’s Catalogue, p. 28, No. 1102. 
Hab. Lao. 
This shell resembles some of the alate species of Unio. 

Species 5. (Mus. Sowerby.) 
ANODON RUBENS. da. testd solidd, oblongo-ovali, tu- 
midd, sublevigatd, extus fusco-viridescenti, intis iri- 
descenti, rubra; latere antico breviusculo, semiro- 
tundo, areé cardinali complanata ; latere postico ob- 
longo, termino vix acuminato, supra uniangulato, 
margine dorsali subarcuato, iargine laterali obliquo, 
margine ventrali medio recto, umbonibus tumidis. 
TuE REDDISH ANODON. Shell solid, oblong-oval, tu- 
mid, rather.smooth, greenish-brown outside, irides- 
cent, red within; anterior side rather short, half- 
round, with a flattened cardinal area; posterior side 
oblong, very slightly acuminated at the end, with 
one angle above, dorsal margin slightly arched, 
lateral margin oblong, ventral margin straight in 
the middle, umboes tumid. 
Lamarck, Anim. sans vert., Anodon, sp. 6. 
Hab. River Nile. 
This species is the type of the genus Spatha adopted 
by some authors, but such generic distinctions seem use- 
less, because incapable of definition. 

April, 1867. 
