GASTEROPODS 385 



than we are giving our specimens. They are O. interfossa, a small shell 

 with deep spiral grooves, sharp varices, and deep sutures ; and O. tir- 

 ciimtettta, also small, but heavy, short-spired, with scalloped or crenu- 

 lated outer lip. 



GENUS Cerostoma 



C. nnttdttii. A species belonging to the southern coast of California. 

 It may be recognized at once by two prominent characters : first, a horn- 

 like projection from near the base of the outer lip, and, second^ the tumid 

 varices alternating with rounded knobs. It has no spiral series of lines 

 like those in Pteronotus festivus ; and it has a row of five or six little teeth 

 upon the inner side of the aperture, like those in Ocinebra poulsoni. The 

 anterior canal is closed. It is about two inches long. (Plate LXXII.) 



C. foliatum. A shell somewhat like the last, but almost twice as 

 large, with heavy wing-like varices (three upon each whorl), made up 

 of overlapping plaits. The knobs between the varices are much smaller, 

 while the revolving ribs, though fewer in number than in most of these 

 west-coast murices, are heavy and large. The aperture is oblong, the 

 anterior canal closed. There is a " horn " near the base of the aperture, 

 as in C. nuttallii, but no row of teeth upon the under side of the lip. 

 The color is dingy white. (Plate LXXII.) 



In the waters of Oregon and Washington there are a few trophons and 

 other forms similar to the east-coast genera. These no doubt belong to 

 the boreal and arctic faunal provinces, and have spread over both the 

 Atlantic and Pacific northern regions. 



SUBFAMILY PTTBFTJKHOE 



This is considered a subfamily of the Mnriridce, and the group 

 therefore bears the subfamily termination -ince. There is no 

 vital difference between it and the subfamily Muricince. The 

 operculum in the Purpurince has a lateral nucleus instead of a 

 subterminal one, but beyond this there are no essential differ- 

 ences. The shell of the purpuras is generally heavy and solid, 

 being adapted to a life among rocks which are exposed to the 

 beating of the surf. There is a lack of that extravagant 

 sculptural design so characteristic of the true murices, most of 

 the purpuras being comparatively smooth, in order, no doubt, 

 that they may offer as little resistance as possible to the rushing, 

 seething waters of exposed rocky shores. 



The Purpurince, like some of the murices, when mutilated, 

 exude a reddish-purple fluid. On account of this, the ancient 

 Romans used to gather great quantities of certain Mediterranean 

 forms belonging to these families, place them in large mortars, 



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