VERMETID^. 



73 



You are sliown wliat appears a minute speck of dust. 

 Examine it under a microscope : the wheel of Aurora^s 

 chariot^ with its refulgent spokes, must have been a 

 piece of ordinary workmanship compared with this ; its 

 compactly convoluted shape, fine curved ribs, and en- 

 circling rings of gold call forth an admu'ation which, if 

 expressed with regard to human feelings, might be 

 termed doating ; it unquestionably bears 



" The signature and stamp of power divine," 



Mediterranean specimens of this and the last species 

 are smaller than oiu's ; that from Greenland is still 

 larger, Clark fancied the present shell to be the spiral 

 posterior terminal portion of Caecum trachea ; but that 

 is a very different object. I believe Montagu was 

 acquainted with H. rota, because in a letter of his to 

 Mr. Dillwyn, dated 8th March 1814, he mentions the 

 discovery of a very minute Ammonite-like shell. In the 

 Tui'tonian collection it was named " Cornu Ammonis.^^ 



It is the Skenea tricarinata of Webster, and the Am- 

 monicerina pulchella and (young) A. paucicostata of 

 Costa, 



Family XII. VERME'TID^, D'Orbigny. 



Body tubular : mantle having a circular border, and closely 

 fitting the neck : head snout-shaped : tentacles cylindrical : 

 eyes sessile, at the bases of the tentacles, and placed more or 

 less externally : foot short. Hermaphrodite ? 



Shell tubular, attached or free, usually (perhaps always) 

 spiral or convoluted when young : mouth round : opercxdum 

 horny, circular, and many-whorled, with a central nucleus. 



I prefer following Clark, who placed in the present 

 family the singular genus Cacum., to arranging it among 



VOL. IV. E 



