MELANTHO. 



291 



[*The form known as M. integ-ra has not been found in New 

 England, but for the sake of comparison I give tlie following de- 

 scriptions and figures : — 



Melantho decisa. 



MeJantho decisa. Shell imperforate, elongate- Fig 554. 



ovate, rather thick, smouth, siirtace hardly broken 

 by lines of growth, with microscopic revolving 

 striiE ; greenish, with irregularly disposed bi-own 

 streaks marking the edge of former peristomes, 

 uniformly chalky-white under the epidermis ; spire 

 truncated, one or two whorls of it alone remaining, 

 apex entirely removed ; remaining whorls three 

 and a half, convex, the last equalling two thirds 

 of the shell's length, imperforate; aperture oval, 

 oblique, more than one half the length of the last 

 whirl, bluish-white within ; peristome externally 

 of a darker color, simple, acute, somewhat sinu- 

 ous, its terminations joined hy a thin callus on 

 the parietal wall, entering within the aperture. Length of axis, thirty-seven ; greatest 

 breadth of body whorl, seventeen ; length of aperture sixteen ; breadth, eleven mill. 



Operculum arcuated, convex, horny, concentric, nucleus nearer the columellar margin. 



MelanfJio decisa, var. integra. Shell imper- Fig 555- 



forate, elongate-ovate, quite thick, smooth, 

 surface hardly broken by lines or wrinkles 

 of growth, marked with delicate revolving 

 stria; ; greenish, with darker streak'^, mark- 

 ing the edge of former peristomes, uniformly 

 chalky-white under the epidermis ; spire 

 elongated-conic, apex perfect, acute ; whorls 

 five, convex, the last equalling two thirds 

 the shell's length, imperforate ; aperture 

 oval, narrowed above, oblique, more than 

 half the length of the body whorl, milky- 

 white within ; peristome externally of a 

 darker color, simple, acute, somewhat sinu- 

 ous, its terminations joined by a thin, transparent callus on the parietal wall of the aper- 

 ture, more heavily thickened and white above and below. Length of axis, twenty-four ; 

 greatest breadth of body whorl, fifteen ; length of aperture, fifteen ; breadth, eleven mill. 



Operculum as in M. decisa. 



Female of M. decisa, 

 var. integra. 



Male of Tlf decisa, 

 var. Integra. 



In general terms it may be said that the form . Fig. 556. 



known as M. integra differs from M. decisa hy being 

 more elongated, having a perfect apex, a smaller and 

 Avhiter aperture, and more prominent revolving striae. 

 These characters are only comparative. The two 

 forms are not distinguished by any decided, constant, "^°"°^ "^ ^^ "'"^''■ 

 specific characters. Fig. 556 represents young shells, which are more 

 globose, comparatively, than the more mature ones. 



* The remarks in the brackets are hy me. — W. G. B. 



