182 WEST COAST SHELLS 



for it distinctly resembles a rolled pebble of granite, 

 and the word "lapilloides" means "like a little 

 stone." It might properly be added that this 

 species is so closely related to the last that it is 

 sometimes difficult to certainly separate them, in 

 which case doubtful specimens should properly be 

 referred to A. engonata. An orange-colored vari- 

 ety found on the rocks at San Pedro is called var. 

 aurantia^ Dall. Both of the foregoing species are 

 now considered as varieties of Acanthina spirata^ 

 Blain. 



Acanthina luguhris^ Sby., the Sad Unicorn, 

 {Monoceros lugubre)^ is found in the extreme limit 

 of our territory, though its true home is on the west 

 coast of Mexico. It has a thick, heavy shell, about 

 an inch long. The wall of the aperture is of a 

 brown color, and it is marked with several rows of 

 white tubercles. The little horn near the canal is 

 very distinct. 



It is now our pleasant task to consider a few spe- 

 cies of pure white shells, regularly marked with fre- 

 quent varices. All of them are quite rare, but if 

 you search along the shore you will probably have 

 the good fortune to find one or more of them. 



The first one is shown in Figure 173, 

 and is namjed Epitoniufn {Opalia) bore- 

 alis^ Gld., the Northern Opal-shell. It 

 consists almost wholly of a long spire, 

 composed of about eight whorls, each 

 of which is crossed by eight blunt ridges, 

 or varices. The aperture is entire, and 

 Fig. 173 the rounded lips are sometimes stained 



