64 



CARDIUM pornlosum. 

 TAB. CCCXLM.~F{o.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, 

 var. ^, with spines united through their whole 

 length by a membrane ; and their bases sunk 

 beneath the edges of the sulci. 



Syn. Cardium pornlosum. JJrander, .09. Xa- 

 mark env. de Paris, 207. Hist. Nat. des 

 Anim. sans Vert. VI. 18. 



Strictly speaking*, the smooth spaces between the 

 deep and decussated sidci, can hardly be called 

 costae, they are so flat, or rather, especially in var. j3, 

 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 j)art 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. |S is, if possible, more elegant thau 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 iurnished 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 I 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 I have 

 seen, but not quite so large. 



The var. /3 is unknown at Barton. 



