QUESTIONS ON UNIVALVES. 145 



46. Describe the different groups into which 

 the genus Patella is subdivided. 



47. What is there particularly interesting in 

 the natural history of the Limpet? 



48. What lesson has the poet drawn from 

 their natural history ? 



49. What is the generic character of the 

 Dentalium, and what its distinguishing mark ? 



50. What is the generic character of the 

 Serpula, and its distinguishing mark ? 



51. In what situations are Serpulx found, 

 and under what circumstances ? 



52. What is the generic character of the 

 Teredo ? 



53. W T hat are the reasons for and against 

 retaining the Teredo amongst the univalve 

 shells ? 



54. Describe the work of the Teredo Navalis. 



55. What is the generic character of the 

 Sabella ? 



56. What is the generic character of the 

 Nautilus, and its distinguishing mark ? 



57. What kind of animal inhabits the Nau- 

 tilus ? 



58. What is there remarkable in the natural 

 history of the Nautilus ? 



59. What is the generic character of the Ar- 

 gonauta. 



60. What position does the Argonauta appear 

 to occupy in the chain of nature ? 



61. Describe the habits of the animal inha- 

 biting Argonauta. 



