58 THE NAUTILUS. 
rayed posteriorly, usually somewhat pointed behind, the females dis- 
tinguished from the males by a well-developed basal swelling, and 
the beak sculpture consisting of parallel, curved ridges, which are 
drawn in towards the hinge-line posteriorly, and are more open 
anteriorly. The cardinals are usually compressed, often torn and 
reflected upwards, and the nacre is generally brilliant bluish-silvery, 
becoming richly iridescent behind, but it is sometimes purple. The 
peculiar beak sculpture, much like that of the Tetralasmus group, 
is one of the best characters when not eroded away. 
Mr. Call is right in his criticism on my paper on the Unionide of 
Florida, in which I placed Unio trossulus Lea and U. lepidus 
Gould in the Parvus group. At the time of writing that paper I 
had carefully examined all of Lea’s material, all the general collec- 
tion of the National Museum, much of B. H. Wright’s, Mrs. George 
Andrews’, Wm. A. Marsh’s, Rey. A. Dean’s and my own collection 
of Florida and Georgia Unios of this general type, but had not 
found a specimen old or young that showed the beak sculpture. 
Recently, in examining some specimens of U. amygdalum in Mr. A. 
G. Wetherby’s collection, from Clear Lake, Florida, I noticed that 
the beak sculpture was perfect, and consisted of a double loop, hence 
they cannot be placed in the Parvus group. I may remark, in 
passing, that having seen Gould’s type of U. lepidus, I should un- 
hesitatingly pronounce it the same as Lea’s amygdalum. ) 
Unfortunately, Mr. Barnes’ description of Unio parvus’ is very 
brief and imperfect, and the only figure he gave of it is an outline. 
Much confusion exists concerning this species, and it is often con- 
founded with Unio texasensis ; in fact, Mr. Lea himself has placed a 
lot of specimens of the latter species from northern localities among 
the parvus in his own collection. Unio texasensis certainly extends 
into southern Indiana and Illinois, and well north into Missouri and 
Kansas. In general, U. parvus is smaller than U. texasensis, is more 
inflated and cylindrical, rather more elongated, and has a much 
more evenly rounded posterior region. The latter is almost always 
distinetly pointed behind. 
I cannot agree with all of Mr. Call’s synonomy. I have all of 
Lea’s types of this and related groups before me. U. marginus Lea, 
and U. cromwelli Lea, are probably the same, and are, no doubt, 
members of the Parvus group, but are widely different from U. par- 
vus, in which he places the former, as they are shorter, less inflated, 
2 Am. Jl. Science and Arts, VI, 1823, p. 174, pl. XIII, fig. 18. 
