CHAPTER XL: THE SPIRE SHELLS AND 

 FLOOD SHELLS 



Family Rissoid.^ 



Shell small, top-shaped or elongated; mouth rounded, 

 scarcely channeled. A family of small marine mollusks living 

 on seaweeds, to which they are suspended by a mucous thread. 



Genus RISSOA, Freim, 



Characters of the family. Two hundred species, abundant 

 chiefly in shallow seas. 



R. minuta, Totten, is a smooth, blunt-pointed shell, with 

 rounded, finely striated whorls. It is yellowish brown and 

 clings by a thread to the leaves of seaweeds. Length, J inch. 



Habitat. — New England to New Jersey. 



R. acutilirata Cpr., yV to } inch long, is worthy of ex- 

 amination under a lens. Its brownish yellow surface is marked 

 by sharp intersecting ribs. It is found on seaweed. 



Habitat. — San Diego, Cal. 



Genus RISSOINA, D'orb. 



Resembles Rissoa except that the aperture and operculum 

 are ear-shaped, and the latter has a blade-like projection on its 

 inner surface. Warm coasts. 



R. fenestrata, Schwartz, is a white shell, blunt at apex, 

 drawn in at base, its rounded whorls strongly ribbed longitudi- 

 nally and spirally, making the surface regularly "windowed," 

 as the specific name implies. Length, | to J inch. 



Genus BARLEEIA, Clark 



Shell smooth, spiral elongated; aperture round; operculum 

 not spiral; with internal projection. 



B. haliotiphila, Cpr., may be found in colonies comfortably 

 quartered among the coralline tufts that flourish on the shell of 



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