Melanellidae and Pyramidellidae 117 



nuclear tip rounded and prominent; about ten flattened whorls with 

 two faint lines at middle and one below sutures; sutures fairly 

 distinct; aperture entire, oval, outer lip sharp, columella concave. 



Melanella hemphilli (Dall) PI. 23, fig. 152 



Alt., 5 mm. Shell slender, conic, imperforate; chestnut-brown, 

 polished and pellucid; apex acute, nuclear whorl prominent; about 

 eight flat whorls; sutures distinct, a narrow line below sutures; 

 aperture oval, narrow, entire, outer lip sharp, columella slightly 

 concave. 



Genus NISO Risso, 1826 

 Niso intermpta-os (Sowerby) PI. 23, fig. 153 



Alt., 14 mm. Shell conic-pyramidal, thin, polished, translucent; 

 apex acute, 10 to 11 whorls, body whorls angulate at periphery; 

 color pale cocoa-brown, with occasional flame-shaped patches of 

 darker color; each whorl defined by a fine reddish-brown line; the 

 sharp outer lip of oval aperture outlined by a similar pencilling; 

 resting periods in the growth of the shell marked by reddish lines 

 crossing whorls at sites of previous apertures; base of shell convex, 

 deeply umbilicated by a conical depression; operculum pale yellow, 

 entirely closing aperture. 



Animal white, with long, slender tentacles, black eyes posterior 

 to base of tentacles. Active and mobile, moves backward as readily 

 as forward and can reverse position in its own length. 



Family PYRAMIDELLIDAE 



The name of this family, formed from the name of its genus 

 Pyramidella (Lat., pyramis, pyramid), is suggestive of the char- 

 acteristic shape of the shells which are pyramidal or conic in outline, 

 turriculate, with an auriform or oval aperture and simple outer 

 lip which is usually sharp. The columella may or may not be plicate. 

 The operculum is corneous, adapted in shape to the aperture, and 

 in the case of those species whose columella is plicate, the inner 

 edge of the operculum is appropriately notched. 



The apices of shells of the Pyramidellidae are heterostrophic. 

 The embryonic shell, which forms the nucleus and the first one or 



206 Lat., Nisus, king of "Mega r a ?; interruptus, interrupted. 



