On the Boring Apparatus of the Carnivorous Gasteropods. 113 



of consideration the anterior tooth which it possesses in common 

 with some other genera^ Cyprina has only two cardinal teeth in 

 each valve : another difference consists in the left valve of this ge- 

 nus being provided with a posterior callous tooth which fits into 

 a broad depression in the opposite valve. The Oban shell may 

 be said to have a posterior tooth, as there is a small groove for 

 one of the kind in the right valve, but it does not differ from that 

 of many of the Venuses*. 



The only character which the Oban shell possesses to induce 

 one to consider it a Cyprina is its slight pallial sinus ; but, as be- 

 fore observed, this is general to the Circes, and it even belongs 

 to some of the Venuses. 



I am not aware who proposed the genus Circe ; it is adopted 

 by Mr. J. E. Gray in the Catalogue of the British Museum, and 

 appears to be a good one. 



XVI. — Note on the Boring Apparatus of the Carnivorous Gaste- 

 ropods, and of the Stone- and Wood-burrowing Bivalves. By 

 Albany Hancock, Esq. 



During the investigation of the anatomy of the Eolidce by Dr. 

 Embleton and myself, we ascertained, as appears in the last 

 Number of the ' Annals,^ that the teeth of these animals are com- 

 posed of silex. Directed by this interesting fact, I was induced 

 to examine the nature of the instrument by which the carnivo- 

 rous Gasteropods pierce the testaceous covering of bivalve and 

 other shells. I found this apparatus in Buccinum undatum to be 

 composed of rows of stout, much-curved spines or teeth, of great 

 brilliancy, and as glossy and transparent as glass, and certainly 

 to have no appearance whatever of horny tissue. They are so 

 similar to those of Eolis, that there could be little doubt that they 

 are formed of the same material ; and accordingly, after subject- 

 ing them to the action of acid, such was found to be the case. 

 Their capacity to drill holes in calcareous matter is therefore 

 easily understood, without the necessity of supposing the aid of 

 a solvent requisite, as surmised by Cuvier. 



This result was to be expected after the discovery of the sili- 

 ceous nature of the teeth of Eolis ; but that the wood- and stone- 

 burrowing Bivalves should work out their excavations by an in- 

 strument provided with the same material may, perhaps, appear 

 somewhat startling. Such however I believe is the fact ; a fact 

 which if established will at once explain all the phsenomena at- 

 tending this much-controverted problem. It is not my intention 



* I am acquainted with a greensand Venus which has a posterior tooth 

 and deprcjjsion as large as in Cyprina. 



