1847. | SHARPE ON THE GENUS TREMATIS. 69 
that the entire surface has a finely reticulated appearance : the fissure 
in the ventral valve is small and close to the hinge: shell very thin. 
Length and breadth $ths of an inch. 
Found by Dr. Bigsby in limestone one mile north of Montreal in 
Lower Canada. 
The above description is compiled from Mr. Sowerby’s description 
and figure. The next species, called by Mr. Hall Ordbicula ? filosa, 
is probably the same as this, but not having seen either shell, I have 
not ventured to throw them together. 
3. TREMATIS FILOSA. 
Orbicula ? filosa, Hall, Paleeontology of New York, p. 99. 
**Orbicular ; one valve more or less convex ; apex marginal; sur- 
face radiated with numerous fine elevated thread-like striz, which 
are more or less prominent, depending on exfoliation of the shell ; 
intermediate strize coming in between the others as they recede from 
the beak, but the strize are not bifurcate.’’—Hall. 
Found in the “ Trenton limestone”’ at Middleville, New York. 
This species is given on Mr. Hall’s authority ; I have not seen it, 
nor the figure which will accompany the description in his forth- 
coming work. From the description I suspect it to be the same as 
the T. cancellata last described. Mr. Hall refers it to Orbicula with 
great hesitation, and appears to consider it intermediate between that 
genus and Crania. 
4, TREMATIS PUNCTATA. 
Orbicula ? punctata, Sowerby, Silurian System, pl. 20. f. 5. 
Ovate, depressed, surface smooth, punctations very large. Length 
$ths, breadth 3 an inch. 
Found in the Caradoc sandstone at Chatwell, on the east flank of 
the Caradoc. 
The specimens described by Mr. Sowerby are now in the Society’s 
collection ; they are very imperfect, and do not show the principal 
characters of the genus. Mr. Sowerby placed it in Orbicula with a 
mark of doubt. 
Note, 26th November 1847.—M. Barrande has described two shells, which pro- 
bably belong to the genus Trematis, under the names of Terebratula hamifera 
and Terebratula scrobiculosa : they are found at Beraun, in Bohemia, in a quartzite 
supposed to belong to the Silurian formation: vide Haidinger’s ‘ Naturwissenschaft- 
liche Abhandlungen,’ vol. i. plate 20. figs. 9 and 10. They may perhaps be the 
old and the young shells of one species. 
