968 NODULARIA 
NODUL,ARIA DIGITIFORMIS (Sowerby). 
Shell elongated, slightly arcuate, solid, inflated, inequilat- 
eral; beaks full; outline of dorsal slope curved; anterior end 
rounded; base line incurved but very full behind the middle; 
posterior basal part obliquely truncate; posterior ridge full, 
slightly double, ending below the median line in a narrow bi- 
angulation; epidermis black, smooth; pseudocardinals large, 
ragged; laterals elongated ; nacre white. 
? Length 100, height 37 mm. 
India. 
Unio digitiformis Sowrrsy, Conch. Icon., XVI, 1868, pl. Lxv, 
fig. 333. 
Nodularia digitiformis SIMPSON, Syn., 1900, p. 8090. 
I have never seen this species, which seems something like 
a large, elongated, smooth N. dowglasic. It is more solid than 
that species and is slightly arcuate according to the figure, 
which is probably taken from an old shell. 
Group of Nodularia japanensis. 
Shell solid, elliptical, subrhomboid or oval, biangulate, round- 
ed or pointed behind and often produced at the posterior base ; 
posterior ridge low or scarcely developed; beaks moderately 
full; sculpture zigzag-radial ; surface of the valves concentric- 
ally striate or more or less covered with corrugated, chevron- 
shaped sculpture, which often becomes somewhat nodulous ; 
epidermis greenish and sometimes rayed in young shells, be- 
coming brown or blackish when adult. 
Animal having the inner gills wider than the outer in front, 
equal behind, free from the abdominal sac throughout, united 
to the mantle to the extreme posterior point ; palpi rather large, 
long; mantle double on the border and toothed below; bran- 
chial opening large, with well-developed, brown papillz; anal 
opening large, with small, tubercular papillze on its inner edge, 
covered with wart-like papilla inside; superanal opening not 
closed below. 
