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left valve, and to find the two doubled teeth, so disposed and so grooved, 
as exactly to receive the teeth of the opposite valve : he was also ena- 
bled, by the same aid, to extend the number of species. Having, through 
the kindness of Captain Gardiner, been favoured with many of the 
Doctor’s specimens, and having been also kindly assisted by Mr. Clarke 
and the Rev. Mr. Cleeve, I am able to place before you nine species : 
T. clavellata. T. aliformis. E. sinuata. 
T. costata. T. dcedalea. T. rugosa. 
T. eccentrica. T. spinosa. S. rudis. 
T. clavellata, curvirostra rugosa clavellata major.* Luid. A trigonal 
shell beset with nodular projections, disposed on the disk of the valves in 
rows, in a transverse curved direction : on the anterior side, a sloping, 
slightly rugose surface, widening from the beaks to the anterior point of 
the valves, and ornamented with three crenulated ridges ; the innermost 
of which enclose a long oval area, faintly marked with longitudinal 
striee, and reaching from the beaks nearly to the anterior termination of 
the shell. Beneath the beaks is a small sulcus, apparently for the recep- 
tion of the cartilage. Plate XII. Fig. 3. 
T. costata. A trigonal shell, with frequent rounded transverse ribs, 
passing from the posterior margin to a crenulated ridge, which separates 
the disk of the valves from the anterior or inferior sloping surface, on 
which are, longitudinally disposed, three crenulated ridges, with six 
smaller interposed ; the inner, of the larger crenulated ridges, enclosing 
a flat long oval area, in the upper part of which is the depression for 
the cartilage. Plate XII. Fig. 4. 
The preceding species have been long known on the Continent. The 
person who first found them being a collector, contrived, by exchanging 
them, to obtain a handsome collection of fossils. 
T. eccentrica. A transverse ovate-oblong shell, with transverse, 
obtuse, rugose ribs, eccentrically disposed, and obliquely intersected by 
the lines which mark the growth of the shell. Plate XII. Fig. 5. Spe- 
* Curvirostra a Cardine (si in piano posueris) dextrorsum vel sinistrorsum reflexo, nomen obtinuit. 
