85 
PATELLA. Linn . 
Gen. Char. Univalve, not spiral, more or less 
conical, concave and simple beneath ; margin 
and apex entire. 
1 his Genus includes at present only such shells of Lin- 
nceus’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 gradual succession of forms from one shape 
to the other, therefore, I cannot see the propriety of con- 
‘diluting Genera founded upon the form of the cone only. 
PATELLA latissima. 
TAB. CXXXIX.— Fig. i and 5. 
Spec. Char. Nearly orbicular, flat, smooth. 
Shell very thin, concentrically undulated ; the umbo is 
excentric; the margin forms a very short oval. 
Fig. 1 shows a specimen 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 01ay 9 
it may possibly be roughish, but this f have not been 
able to ascertain ; however, there are characters enough 
VOL. it. 
