CYAMIUM. 257 



Genus CYA'MIUM *< Philippi. PI. V. f. 8. 



Body somewhat compressed : ecccurrent tube scarcely pro- 

 jecting beyond the posterior side of the shell : gills large : foot 

 slender. 



Shell oblong, very inequilateral : teeth, in the right valve 

 one strong and large double cardinal (appearing like two single 

 teeth in immature specimens), and in the left valve two cardi- 

 nals ; each valve has an indistinct lateral tooth on the poste- 

 rior side. 



The type of this genus is a small shell from the Falk- 

 land Isles, which Philippi described in 1845 as Cyamium 

 antarcticum. This is the only species known, unless 

 the British shell which I am about to mention belongs 

 to the same genus. The ligament in both species is 

 external. Loven adopted Philippics genus for our shell, 

 which has a wide European range ; but he did so with 

 some doubt, because it was supposed that the ligament 

 in Cyamium was internal. Forbes and Hanley seem 

 also to have entertained the latter idea : and thev con- 

 sequently proposed a new genus, Turtonia, for the re- 

 ception of the northern species. Messrs. H. and A. 

 Adams, in their most useful and elaborate work, ' The 

 Genera of recent Mollusca/ at first united Turtonia with 

 Cyamium ; but in the appendix they expressed a different 

 opinion, and separated them, on the ground that " the 

 shell of the former is closed at both ends, the ligament 

 is more exposed than in Cyamium, and it is also pro- 

 vided with slightly prominent elongated lateral teeth 

 which are absent in Cyamium" Having several times 

 examined minutely a series of specimens of C. antarcti- 

 cum in the British and Stockholm Museums, I have 

 arrived at a different conclusion; and, after carefully 

 weighing the reasons stated by the able systematists 



* A little bean. 



