OF MOLLUSCA. 21 



8. ACANTHIZA. 



Shell like Purpura ; inner lip concave, simple; outer lip with a 

 strong tooth in front. Operculum like Purpura. — Adams, Gen. 

 Moll. t. 13. f. 7. 



1. A. striata, t. 87 a. f. 9. 



2. A. unicornis, t. 97. f. 2. 



9. SlSTRUM. 



Shell ovate ; mouth narrow, anterior ; inner and outer lips with 

 large teeth contracting the mouth. Operculum oblong. — Adams, 

 Gen. Moll. t. 13. f. 6. 



1. S. ricinus, t. 96. f. 2. 



2. S. dactyloides, t. 96. f. 3. 



3. S. nodum, t. 96. f. 6. 



4. S. horridum, t. 13. f . 4 ; t. 96. f. 11 ; t. 97. f. 5. 



** Shell living fixed in holes in coral. 



10. Magilus. 



Shell of young animal ovate, subglobose, thin ; the cavity simple, 

 gradually filled up, and the whorl produced into a straight line, with 

 a small cavity at the end for the body, so as to keep the animal on a 

 level with the surface of the coral, the solidified shell being left fixed 

 in the substance of the coral. 



The young shell has been called a genus, Leptoconchus, and is 

 said to have no operculum. — Adams, Gen. Moll. t. 14. f. 9. 



1 . M. antiquus, t. 24. f. 5. 



These shells have been taken for Stalactites or mineral concretions, 

 especially when the cavity of the body has been broken off. They 

 live in or on coral. The extension of the shell is to allow the animal 

 to keep its body on a level with the surface of the growing coral, 

 that it may be able to procure its food. It was placed by Lamarck 

 with the Annelides or Worm-shells, and considered by Guettard as 

 a mineral. 



B. Operculum orate ; nucleus small, near the front end of the outer 

 edge, or subcentral within the outer margin. Buccinina. 



11. BUCCTNUM. 



Shell ovate ; spire moderate ; mouth oblong ; outer lip rather 

 sinuous; pillar rounded. Operculum ovate. — Adams, Gen. Mull, 

 t. 11. f. 4. 



* Operculum oblong ; nucleus marginal. 



1. B. undatum, t. 9. f. 4, t. 92. f . 4 ; t. 94. f. 1 ; Forbes $■ Hanley, 

 B. M. t. 44. f. 5. 



