S P O N D 1 L U S. 75 



are totally wanting in that of Ostrea, the affinity 

 between them is exceedingly great. To the divi- 

 sion Pecten^ particularly, the resemblance of the 

 longitudinal ribs and eared hinges is very remark- 

 able. Some species are, however, destitute of ears, 

 and of the exserted beak. 



These shells are attached to rocks at consider- 

 able depths in the ocean, from which they are se- 

 parated with the greatest difficulty. They are 

 often bored by Pholades and marine insects. 



The term g-ttov^vXos is sometimes used for the 

 prickly head of an artichoke, though more gene- 

 rally for the vertebrae of the back -bone, to either 

 of which some likeness may be found in the Spon- 

 dylus. 



