SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
Measurements— 
Ex. 1. Length, 15 mm. Height, 10.5 mm. 
Ex. 2. Length, 10 mm. Height, 8 mm. 
Ex. 3. Length, 12.5 mm. Height, 10 mm. 
Observations—The Victorian specimens appear to resemble 
Portlock’s Arca |Ctenodonta| dissimilis* from the Upper Ordo- 
vician of Tyrone, Ireland, in some particulars, but differ in 
having a sloping or A.-shaped cardinal line. In C. dissimilis 
the hinge line is straight, and the area conspicuous. 
Horizon and Locality—Silurian (Melbournian); in the 
mudstone of South Yarra, type presented by Mr. Spry. Silurian 
(Yeringian); Wilson’s Station, Lilydale, presented by Mr. J. 
T. Jutson; junction of Woori Yallock and Yarra, B 23, Coll. 
Geol. Surv. Vict. [7883 (type), 7884-6. | 
Genus Nucu.ites, Conrad, 1841. 
[Nore.—Certain species from Victoria in the National 
Museum now described for the first time, were labelled as Cucul- 
lella by McCoy, and this name was used in the notes on the 
quarter sheets of the Geological Survey of Victoria. Since 
Conrad’s genus Nuculites is essentially the same as McCoy’s 
Cucullella, and antedates it by some years, it is obviously the 
correct one for adoption. | 
Nuculites maccoyianus, sp. nov., Pl. IT., Figs. 21-23. 
Description.—Shell elongate-ovate; variable in size, and to 
some extent in form. Cardinal line sinuously arched, ventral 
margin gently and evenly curved, rounded off abruptly at the 
anterior border; posterior extremity rounded, sometimes com- 
pressed, narrow and flange-like. | Cardinal area having the 
characteristic taxodont hinge. Surface moderately convex. 
highest just below the beaks; the latter are usually depressed 
and situated sub-anteriorly, projecting slightly forward. Each 
valve carried an anterior buttress or clavicular ridge immedi- 
ately in front of the umbones, and there is a distinct posterior 
adductor impression midway between the beaks and the pos- 
terior margin. The specimens found are practically in the 
form of internal casts and moulds, but the latter show indica- 
tions of a surface ornamentation of concentric ruge or lines of 
growth. 
* Rep. Geol. Londonderry, 1843, p. 428, Pl. XXXIV., Fig. 5. 
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