69 
• delumbis, 
Conrad , 
ebenus, 
Lea , 
f gracilis, 
Barnes , 
fragilis, 
Raf. 
^ Symph^nota graci- 
Lea, 
fragilis, 
Swainson, 
flavus, 
Raf. 
rubiginosus, 
Lea, 
f sinuatus, (very old,) Raf. 
| phaseolus, 
Hildreth, 
fasciolaris, 
Raf, : 
{ mucronatus, 
| planulatus, 
Barnes, 
Lea, 
L bicolor, ? 
Raf 
flexuosus, 
Raf . 
foliatus, 
Hildreth , 
fasciatus, 
Raf. 
carinatus, 
Barnes , 
furvus, 
Conrad, 
glans, 
Lea , 
glebulus, 
Say, 
Greenii, 
Conrad , 
*heterodon, 
Lea , 
heros, 
S ay, 
multiplicatus, 
Lea, 
interrupts, 
Raf. 
brevidens, 
Lea, 
icterinus, 
Conrad, 
iris, 
Lea, 
inflatus, 
Barnes, 
( siliquoideus, 
( vittatus, ? 
Barnes, 
Raf. 
* This species was first named heterodon by my father, in con- 
versation with Mr. Mason, long before the description was 
published or even written. Mr. Mason communicated the 
name as well as the species to Mr. Lea, who gives his friend 
credit neither for the name nor for discovery of the fact that the 
lateral tooth is double in the right valve, as injustice he should 
have done. I make these remarks, because Mr. Lea insists 
that U. plicatus, Say, must be credited to Leseuer; and, if so, the 
species in question must be called U. heterodon, of Mason, as the 
circumstances under which these two species were described are 
parallel. 
