536 Mr. SowERBY on Cardita concamerata. 



Art. LX. Note on the Cardita concamerata. By G. B. 



SOWERBY, F.L.S.., 8fC. 



It is well known that an anomaly exists in the structure of the 

 Cardita eoncamerata of Lamarck (Chama concamerata of Dill- 

 -wyn). This anomaly consists in the formation of a little cup just 

 -within the ventral margin, and it is formed by a fold of the said 

 margin : it is truly anomalous, for though there are several in- 

 stances among (he univalve shells of Molluscous animals of a little 

 cup formed within the principal portion of the valve, I am not 

 aware of any similar formation to the one under consideration ; 

 for, in the Calyptraiet^ the little cups are only the more or less 

 completely developed rudiments of columellar and inner lip ana- 

 logous to those parts in the spiral univalve. In endeavouring io 

 ascertain the use of the above mentioned little cup, we should 

 naturally be led to -examine the shells of the same genus and 

 family ; this however cannot at present lead to any result, for in 

 no other species does a similar structure exist, and we are not 

 acquainted with any of the animals. The opportunity of examin- 

 ing a single specimen with the dried animal occurred to me some 

 years ago: I then found the two little cups, which are always 

 exactly opposite to each other, filled with very minute globules 

 having the appearance of eggs. I could not, however, form any 

 conclusion from the examination of a single specimen. A late 

 opportunity of examining a number of specimens with the" dried 

 animals within them, enables me now to state that these cups 

 are destined to contain the ovaries, and that the eggs appear to 

 remain in them until they are perfectly developed, and ready to 

 disclose the complete animal with its shell. In some specimens of 

 the shell the little cups are only imperfectly formed : upon this 

 circumstance a question arises, as to whether this cup does or 

 does not, begin to be formed until the impregnation of the ovaries 

 has taken place ; or whether it be not of so rapid growth as to be 

 contemporaneous with the developement of the eggs in the 

 ovaries. G. B. S. 



Jan. 14, 1828. 



