85 
PATELLA. Linz: 
Gen. Cuar. Univalve, not spiral, more or less 
conical, concave and simple beneath; margin 
and apex entire. 
Tats Genus includes at present only such shells of Lin- 
neus’s Genus Patella as have entire margins and are not 
perforated at the apex ; their form varies from nearly flat 
with an umbo to obliquely conical, with a curved apex, 
and there is a gradualsuccession of forms from one shape 
to the other, therefore, I cannot see the propriety of con- 
Stituting Genera founded upon the form of the cone only. 
PATELLA Iatissima. 
TAB. CXXXIX.—Fig. 1 and 5. 
Srec.Cuar. Nearly orbicular, flat, smooth. 
Suet very thin, concentrically undulated ; the umbo is 
excentric; the margin forms a very short oval. 
Fig. 1 shows aspecimen from a slaty Clay impregnated 
with vegeto-bituminous matter, approaching the Kim- 
meridge coal, that occurs in Lincolnshire. The foliated 
form of the Clay seems to arise from the same pressure 
which has flattened the shell so as to crack the margin, 
and make it rather doubtful how flat it would be if 
perfect : the upper surface is still attached to the Clay, 
it may possibly be roughish, but this I have not been 
able to ascertain; however, there are characters enough 
von. 1. (4/6. XXV 
