New Species of Victorian Mollusca. 93 



forms at first a strong convex ridge, wliich gradually flattens and 

 spreads out to a distance from the umbo of two-thirds of the 

 height of the shell, and inclines slightly forward towards the 

 anterior. 



Diine>iswHS. — Antero-posterior diameter, 73 mm.; umbo-ven- 

 tral diameter, 31 mm.; anterior margin, from umbo- ventral 

 diameter, 24 mm.; thickness through both valves, about 10 mm. 



Locality. — Port Albert (Mr. T. Worcester). 



Observations. — This species might at first sight be taken for 

 Zenatia acinaces, Quoy and Gaimard, but it is a good species, 

 and shows many points of difference. The most striking differ- 

 ence is the position of the umbo, which in our new species is at 

 one-third of the length of the shell from the anterior margiu, 

 while in Z. acinaces its position is about one-tlfth the length of 

 the shell; this gives a much larger and more regularly rounded 

 anterior to our shell, and consequently a change in the relative 

 position of the anterior muscular impressions, the cartilage plate, 

 and the transverse ossicle. Z. acinaces also has a straighter 

 dorsal margin, and a more marked ventral siniis, and greater 

 proportional height. 



Type in Mr. Gatliff's collection. 



Modiola victoriae, sp. nov. (PI. XV., Fig.s. 1, 2). 



Description. — Shell elongate-oblong, tumid, with broad 

 umbonal region, a broad and well-marked anterior, and a 

 posterior rather remarkable for its uniformity of height ; ventral 

 margin but slightly sinuated, but the shell in this region above 

 the margin is distinctly constricted. Umbos tumid, only 

 slightly separated, and strongly incurved towards the antei-ior ; 

 lunule ill-defined, scarcely excavated ; anterior margin regularly 

 convex from the umbos to the ventral margin, post-dorsal 

 margin short and convexly rounded to the posterior margin. 

 The absence of any angulation in the outline is a distinct 

 characteristic. 



The colour is a rich dark brown, with the umbo-ventral convex 

 keel of a lighter shade. The surface is marked by irregular 

 lines of growth and fine parallel striae, with faint radial striae ort 

 the anterior region, tending to betome obsolete posteriorly. 



