THE FRESHWATER MOLLUSCA OF VICTORIA 
133 
Vernacular Name.— The Little Knife-shaped Mussel. 
Delessert’s figure is that of a juvenile. In 
very young specimens the uneroded umbones are distinctly 
wrinkled. When w'orking at this extremely variable form in 
conjunction with Cotton, we examined a very large series 
from several localities, and after careful study arrived at 
the conclusions indicated in the above synonymy. Iredale 
differed, but, after closely studying his remarks, \ve hold to 
our original opinion. 
Propehy ridella narracanensis Cotton and Gabriel. 
(PI. IV, Fig. 42.) 
1932 Propehyridella narracanensis C. and G., Pr. Roy. Soc. Viet., xliv, 
(n.s.), Pt. 2, p. 159, pi. 16, fig. 8. 
1934 Propehyridella nepeanensis narracanensis C. and G. Iredale, Aust. 
Zool., viii, Pt. 1, p. 74, pi. 5, fig. 13; pi. 6, fig. 13. 
Size of Type. — Length, 15 5 mm.; breadth, 25 3 mm. 
Localities . — Karracan River, at Thorpdale, Gippsland 
(Type, Nat. Mus., Melb), collected by W. Kershaw; Birre- 
gurra. 
Vernacular Name . — The Narracan River Corrugated 
JMussel. 
Observations . — A small, dull, yellowish-brown species; the 
Birregurra examples are darker and a little more inflated, 
but otherwise inseparable. 
Iredale remarks; “The species named narracanensis by 
Cotton and Gabriel is undoubtedly the very juvenile form of 
the specimens regarded by them as nepeanensis.’ ^ With this 
opinion W'e cannot agree. Re-examination of our material 
endorses our conviction that the two are definite species ; they 
differ consistently in contour and the umbonal wrinkles are 
of dissimilar design. We cannot conceive that narracanensis 
could develop into the robust nepeanensis, which has a 
comparatively square or truncated anterior end. 
Genus PROTOHYRIDELLA Cotton and Gabriel, 1932. 
Protohyridella glenelgensis (Dennant). 
(PL IV, Fig. 43.) 
1898 Unio glenelgensis Dennant, Pr. Roy. Soc. Viet., x, p. 112, pi. 4. 
1900 Diplodon (Hyridella) glenelgensis (Dennant). Simpson, Pr. U.S. 
Nat. Mus., xxii, p. 889. 
1914 Diplodon glenelgensis (Dennant). Simpson, Cat. Naiades, iv, 
p. 1290. 
