NERITACEA. MOLLUSCA. NATICA. 239 



NXtica flava. 



Shell thin, sub-globose ; aperlure large ; inner margin sinuoxis ; 

 umbilicus none. 



Figure 162. 



State Coll., No. 44. 



Natica flava, Gould ; Silliman's Journ., xxxviii. 196. 



Shell of an inflated, globular form, light and thin, white, with 

 a bright straw-colored or golden epidermis ; surface very minutely 

 checkered with very faint, revolving lines, and lines of growth ; 

 spire very little elevated, composed of four rounded whorls, a 

 little compressed behind, near the suture, which is faintly im- 

 pressed ; aperture occupying one half the front aspect of the shell, 

 broad oval, modified by a curve which looks as though it might be 

 caused by a contraction and obliteration of the umbilicus ; outer 

 margin very sharp ; umbilical region about the middle of the left 

 margin much retreating, and deeply indented in most specimens, 

 though evidently never open ; a thin callus, commencing at the 

 upper angle, expands and thickens over this region, then, narrow- 

 ing, forms a thick, rounded, ivory, vertical maigin to the front of 

 the shell. Length about 1 inch, breadth a little less. 



From the collection of Colonel Totten, who obtained it from 

 the Bank fishing grounds. 



The aspect of this shell immediately suggests the Helix aperta, 

 Born, (H. nalicoides, Drap.,") to which it bears a very striking resem- 

 blance in shape. If the existence of an umbilicus is an essential 

 characteristic of the genus, and so it is laid down by Lamarck, this 

 shell cannot come under it. There is no approach to an umbilicus, 

 even in the youngest specimens, the space intended to be occupied by 

 one having been apparently thrown into the aperture. There is one 

 other described species conforming to the same type, the N. Jluctuat.a, 

 Sowerby [Tankerville Catal., p. 12), and figured by Dr. Jay in his 

 " Catalogue, 1836," under the provisional name of N. impcrforata. 

 Their form is so peculiar that Mr. Sowerby has recently grouped them 

 with several others in a new genus, which he calls Globulus. Swain- 

 son employs the word Globularia as having a better termination. 



