04 
CARDIUM porulosum. 
TAB. CCCXLVI. —Fig. 2, 
Spec. Char. Orbicular, anteriorly obscurely 
truncated* longitudinally sulcated, with a 
row of erect, approximate spines, united 
near their points, alternating with each sul- 
cus ; sulci terminated by ligulate teeth ; 
hinge line straight. 
Tar. ( 3 , with spines united through their whole 
length by a membrane ; and their bases sunk 
beneath the edges of the sulci. 
Syn. Cardium porulosum. JBrander, 99. La- 
mark env. de Paris , 207. Hist. Nat. dcs 
Anim. sans Vert. VI. 18. 
Strictly speaking, the smooth spaces between the 
deep and decussated sulci, can hardly be called 
costae, they are so flat, or rather, especially in Yar. /3, 
concave along the middle ; upon these spaces are placed 
rows of erect almost cylindrical spines at very small 
distances from each other, and these spines are united 
for a great part of their length by a thin expansion of 
their sides, leaving their bases and extreme points free, 
forming little arches, a construction that is as elegant as 
it is remarkable ; the long, canaliculate, marginal teeth, 
whose parallel sides render them quite unlike the teeth 
of a saw, are largest, and the series of united spines 
are highest upon the posterior side of the shell. The 
var. (3 is, if possible, more elegant than the a ; it is cer- 
tainly much neater, although the pores between the teeth 
are filled up : the edges of the deep narrow sulci that 
characterise this variety are considerably elevated, very 
even, and sharp ; this var. has frequently more trans- 
parency, and a deeper colour (resembling what is tech- 
nically called green ivory) than the other. Both varieties 
in the young state, or what is the same thing, near the 
umbo, are furnished with granules only in place of the 
united spines. 
Found at Barton, but not very commonly, and very 
rarely approaching perfection : in the neighbourhood of 
Paris it occurs abundantly, and in a good state of pre- 
servation, yet 1 have not met with one so large as this 
figure from an individual kindly presented to me by Miss 
Beminster : Miss Dent has the finest specimen f have 
seen, but not quite so large. 
The var. /3 is unknown at Barton. 
