314 Miscellaneous. 



MISCELLANEOUS. 



On the Anomalous Oyster-Shell. By Prof. J. S. Henslow. 



To the Editors of the Annals of Natural Histori/. 



nitcham, Hadleigh, Suffolk, March 8, 1855. 

 Gentlemen, — In your Number for February, Mr. Busk has 

 m^^ted attention to a curiously-formed valve of a shell, resembling a 

 combination between an Oyster and a Pholas. He intimates, %vith 

 doubt, that the oyster has somehow encased the Pholas, or at least 

 that the shell of the latter is present in that of the former. I sus- 

 pect, however, such may not be the case, and that Mr. Busk has the 

 genuine shell (one valve) of an oyster only. A specimen of a fossil 

 oyster which I prepared for the Ipswich Museum a few weeks ago, 

 seems to explain Mr. Busk's puzzle. This shell had attached itself 

 by the lower valve to an Ammonite, and, as it grew, had taken, in a 

 very complete manner, the impression of its whorls. But the curious 

 result has been, that the npjjer valve, which was not in contact with 

 the Ammonite, has become partially modelled to represent it. Thus 

 the two valves together have the double impression of the Ammonite, 

 in intaglio below, and in cameo above. I suspect from this that Mr. 

 Busk's oyster had grown with the lower valve (which he does not 

 possess) attached to the outer convex surface of a Pholas ; and that 

 the upper valve (the one in question) has in consequence been par- 

 tially modelled after it. We must suppose in these cases that the 

 mollusk accommodates itself to whatever cunature is impressed upon 

 the lower valve, and then the materials secreted for the upper valve 

 will necessarily follow the contour thus given the animal. It may be 

 worth while to search for oysters attached to shells and rugged stones, 

 to see whether traces, more or less distinct, of this sort of impress be 

 not more frequently given to the upper valves than we have sus- 

 pected. I have placed the fossil specimen alluded to in a vertical 

 position, with impressions in clay (one on either side), from the 

 surface of each valve ; that from the lower side perfectly restores the 

 form of the Ammonite, which has been only faintly impressed on the 

 upper. The specimen is probably a detrital relic obtained from the 

 drift. It was purchased by R. Cobbold, Esq., many years ago, iu the 

 north of Suffolk. 



I remain, Gentlemen, yours very truly, 



J. S. Henslow. 



Description of a New Species q/Corynactis. 

 By William Thompson. 



CoR\NACTIS HETEROCERA. 



Spec. Char. — Coriaceous ; the tentacula iu each row varying in 

 shape, the animal but slightly mutable. 



This Corynactis measures nearly an inch in diameter, and the same 

 in height, when in a state of expansion ; when contracted it has the 



