SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
Affinities —Edmondia obliqua, J. Hall* and E. subovata, 
J. Hall,t bear certain close relationship to our species. They 
both differ, however, in general shape, the former being sub- 
quadrate, and the latter lacking the obliquity of the umbonal 
ridge. Both the above-mentioned species were from the 
Chemung Group (Upper Devonian) of the State of New York. 
Measurements.—Length of type specimen, 22 mm.; greatest 
height, 15 mm.; thickness of the two valves, about 8 mm. 
Horizon and Locality.—Silurian (Melbournian). In pale 
mudstone, Yarra Improvement Works, 8. Yarra, and the dark 
indurated mudstone of the Domain-road sewerage cuttings, 5. 
Yarra. Not uncommon. The type specimen presented by Mr. 
F. P. Spry. [7876 (type), 7877, 2239. ] 
[Genus incerta sedis. | 
Genus Spuenotus, J. Hall, 1885. 
Sphenotus warburtonensis, sp. nov. Pl. I., Fig. 10. 
Description —{ Details from an internal cast.] Elongate- 
ovate; anterior extremity short, posterior broad and compressed. 
Beaks prominent, sub-anterior; a well-marked umbonal 
ridge running from the beaks to the post-ventral border. 
Cardinal line nearly straight; area having several long, undulose 
and thin lateral teeth, posteriorly, and two short cardinal teeth 
beneath the beak. Ventral margin sinuous, incurved towards 
the middle, where it meets a conspicuous cincture in front of the 
umbonal ridge. Shell compressed beneath the beaks, and with 
the margin rounded to the ventral border. A strong adductor 
impression occurs under the beaks, situated half-way to the 
ventral angle. Surface of cast marked by strong lines of growth 
at wide intervals, shown as deep groovings. 
Measurements.—Length, 58 mm.; height, 25 mm.; depth 
of valve, 6 mm. 
Observations.—The above species is typical of the genus in 
all essential details. It differs from Modiolopsis, to which genus 
it might otherwise be readily referred, in having the charac- 
teristic lateral teeth and anterior cincture. 
It is noteworthy of this genus that elsewhere, as in England 
and N. America, it has hitherto only been recognised in the 
Devonian; but its occurrence here, in one of the highest beds of 
the Victorian Silurian, is not surprising, since we already know 
* Pal. N.Y., Vol. V., Pt. I., 1885. Lamell, II. p. 388, Pl. LXIV., Figs. 15, 16, 23. 
f Ibid., p. 389, Pl. LXIV., Figs. 10, 18-21, 26-28. 
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