132 MOLLUSCA FROM THE CRAG. 



CYAMIUM.* Philippi, 1845. 



CYAMIUM? Loven, 1846. 

 TURTONIA? Hanley, 1849. 



Generic Character. Shell ovate, equivalve, inequilateral, closed, small, and thin : 

 externally free from ornament. Hinge with two cardinal teeth. Palleal impression 

 entire. Ligament internal. 



This genus has been proposed for a species found in the Antarctic Seas, with an 

 internal ligament, and was adopted by Dr. Loven for the little shell called Mya 

 purpurea by Montague, which has however been erected into a genus by the Authors 

 of the ' Hist, of Brit. Moll.' under the name of Tartonia, in consequence of its having 

 an external ligament. 



CYAMIUM ? EXIMIUM, 8. Wood. Tab. XI, fig. 5, a, b. 



Spec. Char. Testa minima, ovatd, transversd, incequilaterali, l&vigatd, tenui ; postice 

 longiore, utrinque rotundatd ; cardine bidentato, uno laterali remoto pone lig amentum ; 

 apicibus prominentibus. 



Shell small, ovate, transverse, inequilateral, smooth and thin ; posterior side the 

 larger, both sides rounded. Hinge with two cardinal teeth, and one remote lateral 

 tooth behind the ligament ; umbones prominent. 



Length, ^th. Height, T ^th of an inch. 



Locality. Coralline Crag, Sutton. 



One specimen of a species that appears to possess characters most in accordance 

 with the diagnosis of this Genus, is in my Cabinet, and I am induced to place it 

 here provisionally until some more shall be found, either to establish its right to 

 the position, or to remove it ; the desire that everything found in the Crag should 

 be brought under notice must be advanced as an apology for the introduction of some 

 few imperfect materials here, as well as elsewhere, in this Monograph. 



Our shell has an undoubted right to be specifically removed from Mya purpurea, 

 Mont.., though in some of its characters there is a resemblance. The specimen 

 figured is the left valve ; it has two distinct, rather prominent, soft teeth close to the 

 umbo on the anterior side of the ligament, one standing at right angles to the length 

 of the shell, and the other, a larger one, diverging towards the anterior side, with 

 a sufficient space between them for the insertion of a tooth which the opposite valve is 

 supposed to possess : behind these teeth is a depression, where it is presumed the 

 ligament was placed, and if it were so, it must have been wholly internal, and invisible 



* Etym. Kvafiiov, a little bean. 



