978 NODULARIA 
Unio dugasti Morier, Jl. de Conch., XL, 1892, p. 86; XLI, 
LSOQ3, P-. 150; Plawa, tigate 
Unio jaculus ROCHEBRUNE, Bull. Soc. Phila., 1882, p. 44. 
Oxynaia jacula Haas, Con. Cab., Unio, 1910, pl. xv, figs. 5-6. 
Remarkable for its greatly alternated pseudocardinals and 
laterals and silvery nacre. There are two shells of Unio 
dugasti Morlet from the Mekong River, in the National Mu- 
seum, which differ from J,ea’s shell only in being smaller, a 
little less solid and inflated, and in having a lighter colored 
epidermis. I believe them to be the young of N. sagittaria. 
Group of Nodularia cerulea. 
Shell elliptical, inflated, pointed about on the median line 
behind, the post-basal region produced, with a well-developed 
posterior ridge; beaks sculptured with numerous fine, radiat- 
ing riblets, the central ones of which join below, the whole 
often more or less zigzagged and extending well over the 
disk ; epidermis generally bluish-green. Animal unknown. 
NoODULARIA CERULEA (Lea). 
Shell somewhat elongated, subinflated to inflated, inequilat- 
eral, rather thin; beaks moderately full, sculptured with radial 
ridges, which are somewhat zigzagged; anterior end rounded, 
sometimes produced slightly above ; base line straight or lightly 
curved, full behind the middle and obliquely truncate behind 
to the somewhat produced posterior point ; posterior ridge well 
developed; sometimes slightly double, ending in a point about 
on the median line; surface with delicate, irregular growth 
lines, and often having radiating folds on the posterior slope 
and the anterior end; teeth lamellar, delicate, the pseudocar- 
dinals somewhat elevated; muscle scars shallow; nacre bril- 
liant silvery-bluish, iridescent behind. ‘The exterior of the shell 
varies from ashy to bluish-green or nearly blue and is generally 
dull. 
Length 46, height 22, diam. 17 mm. 
Length 4o, height 21, diam. 14 mm. 
Length 26, height 13, diam. Io mm. 
India; southeast Asia. 
