truncatellid-e:. 133 



melania, and that the true place of the genus Truncatella is 

 among the Phaneropneumona Opisophthalma, or the family Aci- 

 culidce (Truncatellidce). 



This genus is well defined by the formation of the shell, if we 

 exclude those species ascribed to it by Philippi and C. B. Adams, 

 which have not the shell turrited and truncate, and the peri- 

 stome of which is disj oined and sharp. The shells of every true 

 Truncate/la are turrited and pointed when young, and show a 

 larger number of whorls than the adidt ones, which are trun- 

 cated and have the apex covered with shelly substance. The 

 operculum is described by some authors as spiral, by others as 

 plain and not spiral ; but the truth is, that there will be found 

 a basal nucleus with the indication of a spiral volution. 



The whole of the species have a very similar appearance, and 

 the distinction of them is rather difficult, because many species 

 are extremely variable in sculpture, showing every gradation 

 from a smooth to a distinctly ribbed shell. But the shape of 

 the mouth and the formation of the peristome, the convexity of 

 the whorls, together with the basal crest, which is well deve- 

 loped in some species and entirely wanting in others, are the 

 principal characters upon which the distinction of the species 

 ought to be founded. 



1. Tbuncatella valida. B.M. 



Shell rimate, rather cylindrical, regularly and slightly attenu- 

 ated towards the truncate apex, solid, whitish, pale yellow or 

 reddish, sculptured with close-set, elevated, rectilinear, obtuse 

 ribs, which are as broad as the interjacent spaces; remaining 

 whorls five, moderately convex, the last furnished at its base 

 with an arcuate compressed keel ; aperture perpendicular, rather 

 obliquely ovate, angular above; peristome double, thickened, 

 slightly auriculated at its upper angle, with the columellar 

 margin very slightly arcuate. Length 9\, breadth 3 mill. 



Truncatella valida, Pfr. in Zeitschr.f. Malac. 1840, p. 182. n. 1 ; 

 Mon. Auric, p. 184. 

 Jay, fatal, 1850, p. 253. n. 5779. 

 Ktister, Mon. p. 11. n. 7. t. 2. f. 7, 8, 19-21, 23. 

 II. and A. Adams, Gen. ree. Moll. ii. p. 311. 



Hah. Philippine Islands, Baclayon, Capul (II Cuming) ; Now 

 Caledonia and Malacca (Dr. Traill). 



The young shell is turrited, pointed, with nine rather convex 

 whorls; last whorl keeled, and smooth below the keel. Length 

 7i mill. 



