Victorian F<h^sils, Part XVL 107 



Cardinal aspect of shell similar to Davidson's figure 21r/. of Gi/ji/r/ula 

 (" Pe7itamerus ") galeata, Dalman sp..i but more strongly, although 

 simply, plicate. 



Measurements. — Length of shell (l)eak to anterior), 19 nnn. > 

 width, 21.5 mm. Greatest depth of l)rachial valve. 5.25 mm. ; ditto 

 of ventral valve, 12 mm. 



Observations. — The above species is represented by a perfectly 

 preserved cast of the shell, which, as it still retains the minute 

 characters of the growth-lines, must l)e regarded as superficially 

 replacing part of the shell itself. 



Gypidula victoriae is closely related to Q. galeafd, Dalman sp.,- 

 a characteristic Silurian fossil having an extensive vertical range. 

 The latter is found in the Wenlock and Ludlow in England ; the 

 Gotlandian in Scandinavia; the newer Silurian in Bohemia; lower 

 Helderberg in the United States; the Devonian of the Ural Moun- 

 tains; and in the Middle Devonian of the Eifel, Germany. 



The chief differences between the Australian and the other widely 

 distributed species are, the greater gibbosity of the umbo of the 

 ventral valve; the comparative flatness of the brachial valve; and 

 the vellicate or pinched-up character of the plications, with a cor- 

 respondingly strong flexure of the sinus and fold of the median area. 

 That this Australian species is clearly referable to Gypidula, J. 

 Hall, and not to Sieherella, Oehlert, is shown by the discrete 

 character of the septum in the brachial valve seen in the present 

 specimen . 



Occurrence. — Silurian (Yeringian). In mudstone, near Lilydale 

 (Ruddock's Quarry). Collected and presented by W. J. Parr, Esq. 



Fam. Atrypidae. 



Genus Atrypa, Dahnan. 



Atrypa reticularis, Liniie sp., var. decvrrens. var. nov. 



Plate XL, fig. L3. 



Description. — Shell sub-circular to long ovoid; ventral valve 

 depressed, brachial valve tumid in the median area, but not so 

 ridge-like as in typical examples of A. imhricata. Ornament con- 

 sisting of radiating riblets crossed by conspicuous concentric lamellar 

 folds. 



1 Mon. Sil. Brach. (Hal. Soc), pt. vii., No. 2., 186:, pi. xv., fi),'. eia 



2 Atrijpa gateata, Dalman, Kongl. Vetensk. Acad. Handlin^ar, 1S27, p. 130. Pentamerxts 

 qaleatus, Dalman sp., Davidson, Mon. Sil. Brach. (Pal. Soc), pt. vii.. No. 2, 1867, p. 145, pi. xv. 

 fists. 13-23. 



