31 
PRODUCTUS liemisphflericus. 
TAB. CCCXXVIII. 
Spec. Char. Hemispherical, longitudinally 
striated ; striae tine ; lower valve very con- 
cave. 
T his Productus appears to be quite free from spines : 
it is much wider than long, and has a straight back as 
long nearly as the shell is wide : there is but a small 
space between the valves for the animal, because the 
lower one is very concave ; the sides are slightly corru- 
gated, otherways the general contour is characteristically 
regular. 
The larger specimen is from some part of Wales, by 
favour of my kind friend Dr. Williams, Reg. Prof, and 
the others from Mynidd Careg, near Kidwelly, in Car- 
marthenshire, through the kindness of Mr. Richard 
Taylor. They are both from Mountain Limestone, as I 
believe the whole genus is. 
PRODUCTUS coincides. 
TAB. CCCXXIX. 
Spec. Char. Semicircular, gibbose, very finely 
striated ; disk inflated ; back staight, ex- 
tending the whole width of the shell. 
The fineness of the stria?, and form of this shell toge- 
ther, give it the contour of a smoothly combed head of 
