153 
Note on the Presence of the Fossil genus Isodonta, Buv., in the 
English Jurassic Rocks. By Joun Lycert, Esq. 
To James Buckman, Esq., Hon. Sec. to the Cotteswold 
Naturalists’ Club. 
Dear Sir, 
Will you have the goodness to communicate to the Club, at 
their next meeting, that we may claim the genus Isodonta, Buv. 
(Sowerbya, D’Orb.), as an addition to the fauna of the English 
Jura? 
The sole species hitherto described is the Isodonta Deshaysea, 
Buy., from the ferruginous Oolite of the Oxfordian beds of the 
Department of the Meuse. Recently, my good friend Mr. 
Leckenby presented me with a fine specimen of the so-called 
Cucullea triangularis, Phill., from the Cornbrash of Scarborough. 
The resemblance in the general aspect of this shell to the Iso- 
donta of Buvignier was at once apparent ; but it was only upon 
an inspection of specimens in the British Museum, collected by 
M. Tesson, that their identity with the Yorkshire shell became 
a conviction to my mind. Individual specimens vary in their 
elongation and in the degree of angularity at their infero-pos- 
terior extremity: little differences of this kind form the sole 
distinction between the British fossil and that of the Meuse, 
and the Normandic specimens in the Museum differ from each 
other at least to an equal extent. The Cucullea triangularis, 
Phill. Geol. York. i. tab. 3. fig. 31, is from the Coralline Oolite 
of Malton; it is somewhat less elongated than my Cornbrash 
specimen, and agrees more nearly with the figures of Buvignier, 
‘Paléont. de la Meuse,’ Atlas, pl. 10. figs. 30-35, except that 
the figure of Phillips is somewhat more inequilateral from the 
shortness of the posterior slope: in the Cornbrash specimen, as 
in those from Normandy and from the Meuse, this feature is 
less conspicuous; but there can be no doubt that the anterior 
side is always somewhat more produced than the other ; the 
surface is smooth, but with two distant and strongly-marked 
folds of growth. The very tumid figure and incurved umbones 
are the external characters whereby it may be distinguished 
from Tancredia; the test is likewise thicker than in the latter 
genus. At present it does not seem that the Cornbrash shell 
can be separated as a species either from that of the Yorkshire 
Coralline Oolite, from the Normandic specimens, or from those 
