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 Ser- 

 pula, and its distinguishing mark ? 



51. In what situations are Serpulse found, and 

 under what circumstances ? 



52. What is the generic character of the 

 Teredo ? 



53. What are the reasons for and against re- 

 taining the Teredo amongst the univalve shells ? 



54. Describe the work of the Teredo Navalis. 



55. What is the generic character of the Sa- 

 bella? 



56. What is the generic character of the Nau- 

 tilus, and its distinguishing mark ? 



5 7 . What kind of animal inhabits the Nautilus ? 



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 the Argonauta. 



