147 
Pi'odllCtus Flemingii, L.-Gr. de Koninck, 184^7, Keck. Anim. Koss,, I, p. 75, pi. 10, fig. 2, 
,, ,, T. Davidson, 1861, Mon. Brit. Carb. Brack., p. 154, pi. 35, fig. 5-19. 
,, longispinus , F. Boemer, 1863, Zeits. Deutsck. Geol. Gesell., p. 589, pi. 16, fig. 1. 
,, 5 , T. Davidson, 1866, Quart. Journ. Geol. Soc., XXII, p. 43. 
5 , j, F. Eoemer, 1870, Geol. v. Ober-Scklesien, p. 89, pi. 8, fig. 2. 
„ ,, E. Etheridge, Senr., 1872, Quart. Journ. Geol. Soc., XXVIII, p. 333, 
pi. 18, fig. 9. 
„ Fleniiugii, L.-G. de Koninck, 1873, Eech. Anim. Foss., II, p. 24, pi. 1, 
fig. 14. (‘) 
,, lougispinus, F. B. Meek and A. Worthen, 1873, Geol. Survey Illinois, V, 
p. 569, pi. 25, fig. 10. 
,, 5 , F. Toula, 1874, Sitzung. K. Akad. Wissen. Wien, LXX, p. 12. 
,, ,, Idem, 1875, Neues Jakrb. Min., p. 252, pi. 8, fig. 8. 
This species, the general appearance and shape of whicli are variable, 
and the most unlike specimens of which are linked together by numerous 
intermediate varieties, never reaches a great size. It is generally rather 
small and usually transverse. 
The ventral valve is regularly arched, or divided into two more or less 
distinct lobes by a ventral furrow, very variable in breadth and depth, and 
commencing at a short distance from the beak. The beak is small and 
reeurved, rarely projecting over the hinge line. The dorsal valve is more or 
less concave, and is sometimes nearly flat in those individuals possessing no 
ventral furrow ; while in other specimens it is distinctly lobed. All the 
specimens sent me by the Rev. W. B. Clarke belong to the first of these 
varieties. The surfaces of both valves are ornamented with numerous small 
longitudinal ribs, resembling each other, and multiplying either by simple 
bifurcation or by intercalation. Over that part of the visceral region nearest 
the beak are concentric folds, generally more distinct on the ears than on the 
centre of the shell. The ribs of a large number of the European specimens 
bristle with tubular spines sometimes several centimetres in length ; but none 
of the Australian specimens under examination have that characteristic. 
Dimensions . — A fairly perfect specimen of medium size, measures 
seventeen millimetres long, by twenty millimetres broad. 
(') For reference to Synonymy. 
X 
