166 
of Streptorynchus Kcdliana and S. tapajotensis of Mr. Derby seem to me 
sufficiently like certain European varieties of O. cremstria to be considered 
as belonging to that sjoecies. 
Gemis — ORTHISj Dalmcm. 
Orthis resupinata, Martin.' 
PI. X, Pig. 9. 
.Anomioi striatoi, Ure, ]793, Hist. Euthergleu, p. 314, pi. 14, fig. 13, 14. 
Anomites resupinatus, Martin, 1809, Petrif. Derbiensis, p. 12, pi. 49, fig. 13, 14. 
Orthis resupinata, L. G. de Koninck, 1843, Descr. Anim. Foss. Terr. Garb. Belg., p. 
224, pi. 13, fig. 9 et 10. 
striatula, 
australis, 
resupinata. 
35 55 
55 55 
resupinotdes. 
McCoy, 1847, Ann. Mag. Nat. Hist., XX, p. 234. 
Idem, 1847, ihid., XX, p. 234, pi. 13, fig. 4 and 4«. 
T. Davidson, 1861, Mon. Brit. Garb. Brack., p. 130, pi. 29, fig. 1-6, 
and pi. 30, fig. 1-5. 
F. Eoemer, 1863, Zeits. Deutsch. Geol. Gesell., p. 591, pi. 16, fig. 4. 
L. G. de Koninck, 1872, Eecb. Anim. Foss.. II, p. 47, pi. 2, fig. 5 
(for synonymy; non idem Toula, 1875, Neues Jahrb. fiir Min., p. 
137, pi. 7, fig. 9). 
Cox, Pal. Rept. Geol. Rept. Kentucky, III, p. 570, pi. 9, fig. 1. 
This species is capable of reaching a great size, and although speci- 
mens five or six centimetres long are not uncommon in Europe, yet none of 
those which I have examined reached that size; the largest does not exceed four 
centimetres. The shell is usually transverse, oval or elliptical, and its valves 
are convex. The dorsal valve is sometimes gibbous ; its hinge line is short, 
being only about half the transverse diameter. The ventral valve is usually 
not so deep as the dorsal valve ; its middle part is often depressed towards 
the front ; its beak is small and slightly recurved ; its hinge area is triangular 
and small, and provided with a deltoid fissure, not covered. The dorsal valve, 
much more convex than the ventral valve, is also more regularly ventricose. 
The external surface of both valves is ornamented with numerous fine radiating 
^ {Vide R. Etheridge, Junr., Geol. and Pal. Q’land., 1892, p. 244, t. 11, f. 26, 28. There is no doubt that 
De Koninck was in error in referring M’Coy’s Orthis australis to this sj)ecies. It is a valid species, very 
characteristic of our Carboniferous Beds, and is of the same type as the European 0. Michelini, — W.S.D.] 
