SILURIAN BIVALYED MOLLUSCA OF VICTORIA. 
very closely in this respect. The Victorian specimen may also 
be compared with P. fecunda, J. Hall,* although that species 
has a marked depression in front of the umbonal ridge. 
P. tenuistriata occurs in the Hamilton Group in the States 
of New York and Pennsylvania. 
Horizon and Locality. — Silurian (Melbournian). In the 
wdiitish mudstone of Merri Creek, Sects. 2 and 3, Kalkallo, coll. 
Geol. Surv. Viet. B b 3. [967.] 
Family Parallelodontidse. 
Genus Parallelodon, Meek and Worthen, 1866. 
Parallelodon spryi, sp. nov. Plate I., Fig. 3. 
Description. Shell of medium size, subovate; cardinal line 
nearly straight, meeting the posterior border almost at right 
angles, but slightly upturned; ventral border convex, narrower 
anteriorly, and broadly curved posteriorly. Median area 
swollen, rising prominently towards the beaks, which are 
situated sub-anteriorly ; posterior region compressed. Cardinal 
area exposed in the type specimen, showing what appears to be 
the extremity of a series of about six parallel and slightly 
oblique hinge-teeth. Surface of valves grooved concentrically, 
the highest part of the ridges being obliquely striated, the 
striae radiating from the beaks. Indications present of a lar^e 
anterior muscle impression situated close to the cardinal area. 
_ Measurements.— Length, about 26 mm.; height 17 mm • 
thickness of entire shell, 8 mm. 
Observations.—- The presence of a parallel series of anterior 
teeth points to relationship with Parallelodon, sensu stride. 
The genus Macrodon, Lycett, 1845 (nom. emend. Macrodus, 
Beushausen, 1895) t is closely allied, and is regarded by Dali 
as synonymous. The latter genus differs in some slight respects 
such as the obliquity of the anterior teeth. Should both types 
prove to be congeneric, the former name will stand, since the 
latter had been used by J . Muller for a genus of fishes whilst 
Beushausen s name is of much more recent date. 
*Tom. supra cit, p. 336, PI. XLIX., Figs. iq k. 2j 
t Abhandl. von Preuss. Geol. Landesanst n’ f tt ft v,m 
+ Text-book of Palaeontology, Zmel-Eastman, '1900, p. P ' 3<5 ' 
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