32. 



be recolIe6led that in thofe Ipinous or tuberculated fpecimens, 

 fuch appendages are always more delicate and fliarp in their 

 infant (late ; thus in the (hells which have been confidered 

 the ciliare, the ribs rife into (harp membranaceous ridges, 

 and the aculice are flat, and ahnofl equally thin ; in this ftate 

 of growth it is nearly orbicular, but when advanced to the 

 lize of an inch and a quarter, it puts on the fub truncated 

 form, and becomes a little produced on that fide of the front, 

 the fpines lofe their (harp edges, and the larger ones begin 

 to aflume the furrowed appearance. In the more advanced 

 flate, the fpines increafe in length, and become more rounded, 

 but the larger ones are always more comprelled laterally, 

 and more or lefs channeled. 



There is the fame gradation to be traced in Cardium echi- 

 natum, and edulet the latter of which is much more orbicular, 

 and tuberculated in its younger ftages, and like the ciliare is 

 frequently white. Thefe variations have caufed mucli per- 

 plexity, and an unnecellary extenfion of the fpecies ; but 

 with all the varieties before us, we mud conclude the fpi- 

 nosum to be a young aculeatum, and fliould be exceedingly 

 obliged to any c: nchologift who will, by fpecimens, point 

 out to us a dillindlion between the ciliare and the young acu- 

 leatiim of the fame fize. 



In Cardium echinahim there alfo appears a variety which 

 has been confidered a diflindl fpecies, and was (we are 

 informed) named by Doctor Solander fpatiila, from the 

 (liape of its fpines. The echinalum it will be obfervcd has 



the 



