THE SMALLER SEA-SHELLS 



181 



Sound are beautifully frilled and richly painted with 

 brown bands. The shells are strong and heavy, and 

 they have an average length of an inch and a half 

 to two inches. Some are nearly smooth, while others 

 are extremely wrinkled. Though the smooth, white 

 varieties are very plain in their appearance, some 

 of the northern beauties, all frilled and banded as if 

 to attract attention, are worthy of a place in any 

 choice collection of handsome shells. 



Closely related to the Purples are the 

 Unicorn-shells, a small group of mol- 

 lusks which are almost exclusively con- 

 fined to the west coast ot America. 

 Their former name referred to the fact 

 that a little horn is developed on the 

 edge of the outer lip, near the canal, as 

 is well shown in Figure 171, of Mono- 

 ceros engonatum^ Conr., the Angled 

 Unicorn, now called Acanthina engonata. These 

 animals are usually found clinging to rocks under 

 a heavy growth of seaweed. The shells themselves 

 are almost the same color as the stones to which they 

 are attached. The second name of this species was 

 suggested by the fact that the whorls are sharply 

 angled, quite in contrast to those of the next species. 



Acanthina lapilloides^ Conr., the 

 Pebbly Unicorn, {Monoceros lapil- 

 loides). Figure 172, has a very pretty 

 little shell, about an inch in length, 

 with a spire of four whorls, a rather 

 small aperture within which are sev- 

 Fig. 172 eral knobs or teeth. It is well named, 



Fig. 171 



