58 LESSON IX. 



Teacher. And what are the points of dis- 

 similarity, that lead you to separate the smaller 

 set from the whole group ? 



Child. The difference in their general ap- 

 pearance, and in their mouth. 



Teacher. You have now formed a smaller 

 class. Such a subdivision is called a genus, 

 from the Latin word gen us, a kind ; the plural 

 of genus is genera. The characteristic dis- 

 tinction of each genus among the univalves is 

 founded on the general appearance of the shells, 

 and the form of their mouths. The specimens 

 which you have chosen belong to the genus 

 called Conus. You must now examine the 

 shells carefully, and try and discover in what 

 respect they resemble each other; you will 

 then be able to describe their generic charac- 

 ter, or mark those qualities possessed in com- 

 mon by them all, and which distinguish them 

 from all other shells. How will you set about 

 this? 



Child. We must compare them together, 

 and put down those qualities which they all 

 possess. 



Teacher, First consider their general appear- 

 ance. 



Child. Their shape is very similar; it re- 

 sembles a cone. 



Teacher. Yes, aud as their form is conical, 

 they have received their scientific name Conus, 

 and their common English name Cone. 



Child. The name expresses very well the 

 appearance of the genus. 



