146 
Frocluotus UHclcitus, A. d’Orbigny, 1850, Prodr. Pal., I, p, 141. 
,, „ J- Morris, 1850, Cat. Brit. Boss., p. 145. 
,, 5 , M. V. Griiaewaldt, 1860 Mem. Acad. Imp, St. Petersbourg, II (7), 
p. 116. 
,, ,, T. Davidson, 1860, Mon. Scottish Carb. Bracb., p. 4, fig. 15, 16, 17. 
5 , 5 , Idem, 1861, Mon. Brit. Carb. Bracb., p. 161, pi. 30, fig. 7 and 13. 
„ undatus ? Toula, 1874, Sitzung. K. Akad. Wissen. Wien, LXX, p. 9. 
A shell of moderate size, suborhicular or slightly transverse, seldom 
longer than broad. The hinge line is generally a little shorter than the trans- 
verse diameter. The ventral valve is snh-hemispherical, rather regularly 
arched, and with no ventral furrow ; the beak is small, swollen, recurved, hut 
projeeting only a trifle over the hinge line ; the ears are small, and nearly 
rectangular at their extremities ; the external surface is entirely covered with 
thiek concentric folds. These folds are angular and arranged terrace-like one 
under the other ; although nearly parallel to each other their direetion is not 
very regular ; they are, indeed, usually sinuous, and generally their course is 
not unbroken ; they are crossed perpendicularly by a great numhcr of filiform 
ribs multiplying themselves by interposition, and occasionally interrupted by 
a small tubercle, or a small tubular spine. The dorsal valve is concave, and 
follows, at a little distance, the contour of the ventral valve. Its ornamenta- 
tion is like that of the ventral valve. 
Dimensions . — Its length is from fifteen to thirty-three millimetres, and 
its thickness seven to twelve millimetres. 
Horizon and Localities. — This species is met with rather frequently 
in the Ui^per Limestone of Vise, but it seems rare elsewhere. It has been 
found in England, Ireland, Scotland, Central Russia, and the Ural. Mr. 
Tonla records it with doubt from Sj)itzhergen ; Leichert^ and Mr. W. B. Clarke 
found it near the Paterson River, New South Wales, in a brown sandstone. 
Prodtjctus flemingii, Soioerby. 
PI. XI, Pig. 3. 
A.nomice echhiatce, D. Ure, 1793, Hist. Eutberglen, p. 315, pi. 15, fig. 3, 4. 
Droductus Fleniingiiy J. Sowerby, 1814, Min. Concb., I, p. 154, pi. 68, fig. 2. 
,, longisphlUS , Idem, 1814, ibid; p. 155, pi. 68, fig. 1. 
[Dr. Lnthvig Leichhardt. — W.S.D.] 
