3IONODONTA. 



107 



sharp tootli below, and outwardly with a furrow parallel with its free 

 margin. The color is black, with narrow white dense zig-zag curved 

 streaks. The spire is pure black. Oblique alt. 13, diam. 15 mill. 



There are forms with more elevated whorls, departing a little from 

 the usual form. (Philijrpi.) 



Habitat unknown. 



T. neritoides Phil., Zeitschr. f. Mai., 1849, p. 170.— Conchy!. Cab., 

 p. 303, t. 44, f. 4. 



This form may be the some as that I have described below as M. 

 perplexa. It is said to be very blunt in the spire, and differently 

 colored. 



M. PERPLEXA Pilsbry. PL 35, figs. 6-8. 



Shell depressed-conoid, imperforate, oblique, light green, radiately 

 Hamulate above with wide zigzag dark green stripes, more narrowly 

 striped beh)w, encircled about the middle with a well-defined lighter 

 zone ; the entire surface polished, and viarked ivith numerous 

 slightly impressed light-colored spiral lines ; spire vei'v short, conic, 

 acute ; sutures more impressed than usual in this group ; whorls 5, 

 qidte convex, the upper ones ruddy or purplish, the last very large,, 

 slightly compressed just below the suture, gently descending an- 

 teriorly ; aperture very large, very oblique ; outer lip thm, acute, 

 pearly, iridescent, VLwd, apparently Urate within; columella extremely 

 oblique, its inner edge concave, distinctly toothed or hooked below, 

 bearing a shallow groove parallel with the edge, from the place of 

 the umbilicus downward ; columellar area very wide, white. 



Alt. 81, diam. 10 mill. 



Japan. 



This form is very oblique, like M. constellata. From that species 

 it differs in the characters italicized in the al)ove description. There 

 is a distinct ledge within the base, as in M. nigei-rima, ]M. ])orcifera 

 etc. The notch at the base of the columella is more decided than 

 in any other species of Neodiloma, and raises a doubt concerning the 

 true position of the species. The specimens before me were received 

 from the Smithsonian Institution. Compare preceding species. 



M. GUTTATA Koch. PL 34, figs. 16, 17. 



Shell small, narrowly umbilicate, depressed conical, very smooth, 

 upper surface with distant impressed lines, black, subtesseUated 

 with scattered white spots ; aperture rhomboidal, patulous ; um- 



