220 



PROCEEDINGS OF THE ACADEMY OF 



[Dec, 



The operculum is unlike that of any known Neritid snail, but the 

 chief peculiarity of the genus is in the radula. There is no central 

 tooth whatever, the arrangement being as figured by Fischer for 

 Nento'psis, the formula being oo -3-0 3- oo , that of Neritina and 

 Nerita being oo -4-1-4- go . The large inner lateral tooth is low, of 

 very irregular form, without cusp, and hard to see on account of 

 its low relief. The second lateral is also low, narrow, without cusp, 

 and interlocking with the larger lateral. The major lateral {Hut or 

 Schirm'pJatte of German authors) resembles someAvhat that of Neri- 

 tma reclivata as figured by Troschel. The uncini are exceedingly 

 numerous. Only the inner ones are drawn in the figure (fig. 7). 



While the shell has some resemblance to that of Lepyrium, the 

 operculum and radula are very different, and strikingly unlike 

 Neritina (or Theodoxus). 

 Neritilia succinea guatemalensis subsp. Fig. 8. 



The shell is Neritiform, hemispherical, solid, buff, the spire pro- 

 jecting very slightly. Embryonic shell very small, glossy; subse- 

 quent whorls not quite 2, rather dull, and smooth except for faint 

 growth lines and on the latter part some impressed lines. The 

 aperture is semi-circular, yellowish and smooth within, the lip sharp. 

 The columellar margin is straight without teeth or notches. Callus 

 flattened and plain, not very extensive, whitish towards the edge. 



Alt. 3, greatest (oblique) diam. 4.7 mm. 



Alt. 4. greatest (oblique) diam. 5 mm. 



Fig. 8. — Ncrililia succinea (jualemaloisis, sliell and three views of operculum, tlie 



middle one an oblique view of the inside from the outer 



edge, showing greatest height of the ledge. 



The operculum is slightly reddish towards the outer margin, a 

 little concave, marked with growth lines, the nucleus near the basal 

 end of the straight edge. The interior face is covered with a calcar- 

 eous layer except for a reddish border along the outer arc. The basal 

 and columellar margins have a raised ledge, which rises in a rather 

 high summit at the basal end of the straight columellar edge; this 



