SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
beds, near Kendal. In this species the concentric plications are 
not nearly so pronounced as in the Australian form. Another 
species which may be compared with ours is Orthonota undulata, 
Conrad.* This fossil occurs in the Hamilton Group in the 
United States. Although generally resembling our form, it is 
not so convex, and it has the concentric furrows undulate in the 
posterior area of the shell; whilst the portion between the 
umbonal ridge and the post-cardinal slope is more numerously 
relieved by radiating folds. 
Observations.—The Orthonota occurring in the Silurian 
beds at Yass, New South Wales, and recorded by Prof. T. W. E. 
Davidt in his geological section of that district as Orthonota 
rigida ? |Sow. sp.] appears to be a new species, judging froma 
specimen in the National Museum from the Shearsby collection. 
It is not related in any way to McCoy’s Victorian 0. subrigida 
(MS.), which is further on shown to be referable to Nucula 
lamellata. Compared with Orthonota australis, sp. nov., the 
Yass specimen is more compressed, and has a more pronounced 
mesial sinus. 
Horizon and Locality—Silurian (Melbournian), Moonee 
Ponds Creek, Flemington (“ Royal Park”). Two specimens 
collected by the Geol. Survey of Victoria. [7869 (type), 7870|.t 
Family Grammysiide. 
Genus GrammMysta, E. de Verneuil, 1847. 
Grammysia abbreviata, sp. nov. Pl. L., Fig 2. 
Description.—Shell subquadrate, cardinal line arched; 
ventral margin nearly straight, slightly incurved at the junction 
with the umbonal depression, the latter meeting the ventral 
margin a little in front of the median third. Surface of shell 
rather strongly convex towards the beaks, which are sub-anterior. 
A sub-umbonal depression in front of the shell makes a slight 
angularity reaching from the umbones to the antero-ventral 
margin. In the fioured specimen this angularity is emphasized 
by crushing. From the umbo to the postero- ventral margin 
* Conrad, Geol. Survey, N. York,; Ann. Rep., 1841, p. 51, Pl. —., Fig. 6. J. Hall, 
Pal. N. York, Vol. V., Pt. I., 1885. Lamellibranch., II., p. 478, Pl. LXXVIII., Figs. 
gh Ann. Rep. Dept. Mines, N.S. Wales, 1882 (1883). Notes to Section across Silurian 
and Igneous Rocks, Yass. 
+ Registered Nos. in Museum. 
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