ZOOPHAGOUS MOLLUSCA. 311 



as to envelope completely the objects on which they prey, 

 for a long- retention of it in its grasp is necessary from the 

 slowness with which they work their auger or spiniferous 

 tongue. 



It appears to be ascertained that the Bullae are also 

 feeders on the Bivalved Mollusca. Mr. Humphreys men- 

 tions that he had found a species of Mya alive in the gizzard 

 of Bulla lignaria.* Cuvier says that the stomach of the 

 Bullae, in general, is usually filled with the remains of small 

 shells : j- and Mr. Sowerby tells us that they are " exceed- 

 ingly voracious, as is evident from the fact, that the animal 

 of B. aperta is sometimes distorted by having swallowed 

 entire a Corbula nucleus, which is a very thick and strong 

 shell, nearly equal in size to itself." J Now as the Bullae 

 have no perforating instrument in the mouth, nor jaws to 

 crack them, they are under the necessity of swallowing 

 their prey entire, and, as might have been anticipated, there 

 is provided an internal apparatus to supply the deficiency of 

 the oral armature, and break up the shells, so that the inmates 

 may be exposed to the influence of the digestive agents. This 

 singular apparatus is placed within the gizzard, and consists 

 of three strong calcareous pieces, differing in form and size 

 in the different species, thus modified, undoubtedly, to 

 suit them to their peculiar wants, and moved by powerful 

 muscles against each other. § In the Aplysia, a genus of 

 the same natural order (Tectibranches) as the Bulla, we 

 find a curious modification of this structure, accompanied, 

 however, with a total discrepancy in the tastes and pro- 

 pensities of the creature ; and this is a fact which deserves 

 to be remembered in estimating the value of inferences, in 

 relation to the habits of animals, drawn from their presumed 

 affinities. The oral organs of Bulla and Aplysia are nearly 

 the same, and there is a resemblance in their complicated 

 digestive apparatus ; but instead of three shells, the mus- 

 cular gizzard of the latter is studded with numerous 

 sharp pyramidal knobs of a semi-cartilaginous consist- 

 ence, and of unequal sizes, and which may be rubbed off 

 very easily, for they have no muscles to attach and move 



* Lin. Trans, ii. 16. t Mem. x. 14. 



t Gen. Rcc. and Foss. Shells, No. 39. 



§ Cuv. Mem. x. L3. These stomachal teeth (first noticed by Apuleus) 

 were described by Gioeni, a Knight of Malta, and professor of Natural 

 History at Catania, as a new genus of multi valve shells ; a genus retained by 

 Retzius, Bruguiere, and Lamarck, until the fraud was detected by Drapar- 

 naud. See Bosc, Vers. i. 76 ; and Babbage on the Decline of Science, 

 j>. 175. Spalanzani lias given a very interesting notice of the Chevalier 

 Gioeni's Museum in his travels in the Two Sicilies, i. 310, &c. 



