170 



WEST COAST SHELLS 



Fig. 159 



shell, Purpura nuttallii, Conr. {Murex nuttallii and 

 Cerostoma nuttallii)^ Nuttall's Hornmouth. If you 



examine a full grown shell of this 

 species you will find a sharp tooth, 

 or horn, near the base of the outer 

 lip. Some young specimens have 

 no horn, and they may also have 

 an open canal instead of a closed 

 one, which the adult has. Allow- 

 ance must be made tor the age and 

 development of the specimen in 

 determining its name. The shell 

 of an adult of this species is about 

 two inches long, and it is of 

 a dingy white color, somewhat 

 marked with brown. On each whorl are three dis- 

 tinct varices, with rounded knobs between them. 

 This species seems to be quite closely related to the 

 next one, so much so that some have considered one 

 but a variety of the other. 



Purpura foliata^ Martyn {Murex foliatus\ the 

 Leafy Hornmouth, is a more northern species and 

 has a larger shell, which is very conspicuously 

 marked with its three broad, wing-like varices. They 

 appear to be made up of overlapping plates, like 

 shingles on the roof of a house. The canal is con- 

 spicuously curved backward, and at each period of 

 definite advance in the growth of the shell the old 

 canal is left behind and becomes a distinct feature 

 of the specimen. Strong spiral ridges appear on the 

 back of the shell, spreading out in a fan-shaped man- 

 ner upon the varices. A very large specimen dredged 

 near Monterey measured 87 mm. in length and 63 



