165 
Streptorynchus ILalliamiS^ O. A. Derby, 1874, Bull. Cornell Dniv., I, No. 2, p. 35, pi. 
5, fig. 1, 2, 5, 8, 12, 14, 16, 18, and pi. 8, fig. 3. 
5 , Tapajotensis, Idem, 1874, Hid., p. 37, pi. 5, fig. 3, 6, 7, 9, 10, and pi. 8, 
fig. 9. 
,, ,5 F. Toula, 1875, Neues Jahrb. filr Min., p. 252. 
,, „ var. macrocardinalis ? Idem, 1875, Hid., p. 253, pi. 8, 
fig. 5. 
Orthis [Streptorynclms] eximiceformis ? Idem, 1875, Sitzung. K. Akad. Wissen. Wien, 
LXXI, p. 548, pi. 2, fig. 7. 
This shell is rather large when normally develo]Ded, hut is much sub- 
ject to distortion and irregular development. When its growth has not met 
with interference it is rather depressed, suh- semicircular, and broader than 
long. The Australian specimen now under notice answers to this descrip- 
tion. The ventral valve, the only one known, is slightly hut regularly 
ventricose, except for a little depression near the ears ; its hinge line is a 
little shorter than the transverse diameter ; the whole surface is covered with 
numerous filiform radiating ribs, the principal ones originating at the beak, 
and extending from it to the margins, slightly thickening in that direction : 
between these principal ribs, and at a given distance from the beak, secondary 
and thinner ribs arise, one or two of which thicken and behave precisely like 
the principal ribs. All the spaces between these ribs are crossed by concentric 
lines of growth, often slightly undulating, giving the valve a rugose appear- 
ance. This rugosity sometimes extends even to the ribs. 
dimensions. —The specimen I have just described is only twenty-seven 
millimetres long by thirty- six broad. 
dLorizon and Localities. — I am uncertain as to whether the Devonian 
fossils considered by many authors as belonging to this species really do belong 
to it, because most of the specimens so determined, being badly preserved, 
might possibly be only O. umhraculum, Schlotheim, altered or lacking some 
characteristics. I have no doubt that O. spinigera, McCoy, is merely a 
variety of O. crenistria. 0. crenistria is rather rare in the Lower Car- 
boniferous beds, but very abundant in the upper beds of the Carboniferous 
Limestone. The specimens found by Mr. W. B. Clarke come from a brownish 
limestone veined with green, found between Karua and Dungog. In Brazil 
it was found in the limestone at Bonjardin and Itaituba. The characteristics 
