220 SHELLS AND SHELL-FISH. PART I. 



splendid shells, although mostly of a small size, have a 

 brilliancy in the emerald green of their apertures, which is 

 perfectly unrivalled in this family (figAO.) like the Callio- 

 stomce, the basal whorl is convex, more so, indeed, than 



40 ' in an y other of this s e - 



nus, except that to which 

 it leads ; the spire is also 

 generally more produced, 

 and in one species (a) is 

 so long that it resembles 

 a small Turritella. It is among these shells that the 

 most prevalent character of Monodonta appears. The 

 base of the pillar in some forms an angle, and in others 

 a small but very distinct tooth : their exterior is always 

 smooth.* Next to these we place a small group of 

 equally ventricose shells, to which we retain Lamarck's 

 name of Monodonta; they have, in fact, almost the form 

 of Senecti, but they are small, and the pillar is both 

 umbilicated and toothed : in some, these characters are 

 very slightly developed ; in others, they are very strong ; 

 and this variation takes place in species otherwise 

 so much alike, that they might almost be taken for 

 the same at different periods of growth. They are 

 mostly finely granulated, and sometimes striated within ; 

 but their ventricose aspect is altogether peculiar ; the 

 umbilicus is always smooth round its edges, but varies 

 in its size. In the next sub-genus, Fragella, the 

 basal tooth is so large, that its projection, joined with 

 the teeth on the inner margin of the outer lip, gives the 

 aperture an appearance of being distorted. The well- 

 known little shell called the strawberry trochus, is the 

 type ; and, by its depressed form, pointed spire, and 

 large umbilicus, reminds us immediately of a genuine 

 Trofhus : the surface of nearly all is beautifully granu- 

 lated. In our fourth group, or Monilea, the umbilicus 

 and its singular marginal rim are precisely the same as 

 in Chlorostoma, except that the umbilicus is wider, the 



* This beautiful group was well known to Humphrey, whose name, im- 

 posed near forty years ago, we have of course retained, instead of some 

 others recently given by the French nomenclators. 



