998 NODULARIA 
For this group Frierson has recently proposed the new 
generic name of EnsipeNns, (Naut., XXIV, 1911, p. 98). He 
says: 
“The Unio ingallsiana I,ea differs generically from Nod- 
ularia in having little or no beak sculpturing and in having a 
smooth shell. Its cardinal teeth are blade-like and double in 
the right valve and single in the left. The cardinal teeth form 
a part of the general inner part of the shell, not having a 
“fulcrum” (as the buttress-like thickening of the noose sup- 
porting the cardinal teeth, and extending posteriorly to the 
adductor scar, may be called), which is so generally shown in 
most Unionide. ‘The “third anterior muscular scar” is sepa- 
rate from the anterior adductor scar, whereas in Nodularia 
they are always confluent and not easy to differentiate. For 
those shells, as the Unio pas Lea (and imgallsiana Lea), ex- 
hibiting these characters as outlined, the writer proposes the 
new genus EnsipENs. ‘Two other peculiarities of the two 
species named may prove to be of generic significance, but at 
present they may be regarded as being of specific import mere- 
ly. These are the entire confluence of the anterior adductor 
and the ‘‘protractor pedis” muscle scar, and that the escutcheon 
is half way the length of the lateral teeth.” 
NODULARIA youRDYI ( Morlet). 
Shell somewhat elongated, solid, greatly inflated, inequilat- 
eral; beaks full and high, with undulated sculpture; posterior 
ridge not greatly elevated but decidedly angled, curved slight- 
ly downward in the middle; anterior end rounded, somewhat 
angled above; base line curved, fuller behind the middle with 
a long, sloping truncation at the posterior end; posterior point 
above the median line; surface lightly striate; epidermis 
brownish-green; pseudocardinals subsolid, somewhat com- 
pressed; laterals lightly curved; anterior scars deep; posterior 
-scars shallow ; nacre white. 
Length 50, height 24, diam. 22 mm. 
Tonkin. 
