THE SMALLER SEA-SHELLS 



171 



mm. in breadth. The color of all of these shells is 

 a dull white, somewhat obscured by external stains. 

 The present name of this shell goes back to 1784, 

 and has been recentl}^ restored by Dr. Dall. The 

 shells commonly known as Purple-shells will no 

 longer bear the name Purpura, as will be seen by 

 reference to a later page. The purple dye of the 

 ancients was obtained from one or more species 

 of Murex. 



Figure 160 

 gives an excellent 



idea of a rare 

 shell named 'T^ro- 

 phon triangula- 

 tus, Cpr., the 

 Three- cornered 

 Trophon. The 

 shell is quite 

 large, but it is of 

 light weight, ow- 

 ing to the extreme 

 thinness of the 

 varices. Exter- 

 nally it is reddish 

 brown in color, 



though nearly white internally. When examined 

 closely it seems to be almost wholly made up of 

 wings, and one wonders where the animal found 

 internal space enough to enable it to carry on busi- 

 ness. The original young specimen from which the 

 species was named was dredged from the vicinity of 

 Catalina Island at a depth of sixty fathoms. It 

 was less than half an inch long, but adult specimens 



Fig. 160 



