EUC ALODIUM. 3 



Subgenus EUCALODIUM s. str. 



In this group the internal pillar is flattened and strongly 

 twisted to form a spirally ascending plate or lamella (pi. 5, 

 f. 20; pi. 7, f. 2, 12). The columella is more or less abruptly 

 truncate obliquely at the base, as seen in an oblique view. 

 Usually a careful inspection of that portion of the axis exposed 

 by the truncation of the summit will show the form of the 

 pillar (see pi. 8, fig. 17) ; but it is better to expose it by cut- 

 ting a hole in the shell. Only three or four species of the re- 

 stricted subgenus are known. In all of them the cuticle is 

 thin and generally lost in adult shells. 



I. Solid, strong-shelled species. 



1. Very large, length 70 to over 80 mm., with sculpture 

 of coarse, low, waved wrinkles; pale brown or 

 dark red-brown. 



E. decollatum,, and var. ghiesbreghti. 



2. Smaller, length 52 mm., with close, low rib-strias; 

 white. E. compactum. 



II. Rather thin, weakly wrinkle-striate, flesh-colored or 



fleshy-brown; length 32-55 mm. E. mexicanum. 



E. DECOLLATUM (Nyst) . PL 4, fig. 9 (type figure) ; pi. 1, fig. 1. 



Shell thick, pale ashen, turreted-cylindric, the apex trun- 

 cate, base subumbilicate ; whorls a little convex, striate ; aper- 

 ture suborbicular ; columella one-folded; lip reflexed. 



It is cylindrical, turriculate, the shell though thick is sub- 

 diaphanous. The spire is formed of 10 narrow T , slightly con- 

 vex whorls, covered with longitudinal, slightly oblique stride, 

 more pronounced near the sutures, which are simple and not 

 deep. The summit of the spire is truncate, as in Bulimus 

 decollatus. The last whorl is very short, convex beneath, and 

 pierced by an umbilical chink which is not deep and is wholly 

 closed. The aperture is large, orbicular, detached from the 

 rest of the shell, and is a little oblique to the axis. Columella 

 provided with a fold in the middle, comparable with that of 

 the Clausilias. The color of the shell is ashen-brown. The 

 apertural side of the shell is much worn. Length 75, diam. 

 20 mm.' 



State of Tabasco, southeastern Mexico. (Ghiesbreght.) 



