76 University of Michigan 



irregular. The shell is rendered imperforate by a slight, 

 thickened reflection of the columella in the parietal region, 

 where it is continued by a thin callus that connects the ends 

 of the peristome. 



Measitrements 



alt. maj. diam. alt. apert. diam. apert. whorls 



Gibbons (1879) 12.0 54(6.5) 58(7.0) 64(4.5) 4 



Cb6 (dead) 9.3 52(4.8) 60(5.7) 65(3.7) 3i^ 



Cll (dead) 13.5 57(7.7) 65(8.8) 66(5.8) 3i^ 



Cll (dead) 11.4 56(6.4) 70(8.0) 64(5.1) 31^ 



Bb5 (living) 9.3 57(5.3) 65(6.0) 67(4.0) 3 



The radular formula (fig. xiv-48) of a medium-sized speci- 

 men is 24-1-24. The central tooth is symmetrical and tri- 

 cuspid. The 1st to 7th laterals are asymmetrical but also tri- 

 cuspid ; the entocone is small, slightly below the level of the 

 mesocone, and is obscured by the refraction of the edge of the 

 tooth. All of the cusps are elongate and very sharp. The 8th 

 lateral usually adds a minute, outer, 4th cusp. Beyond this, 

 the number of cusps becomes very variable, as is illustrated 

 by the three figured examples' of the 14th tooth, which occur 

 within four consecutive transverse rows. The 24th tooth is a 

 mere denticle. 



The jaw (fig. xiv-49) of the same specimen is double, and- 

 consists of a rounded-oblong, emarginate, basal plate and the 

 recurved, arcuate true jaw. The latter bears a triangular 

 median thickening or low rib, and two, transverse, lateral ones ; 

 these slightly undulate both margins of the recurved portion. 

 The outer surface is closely, but irregularly, striate; these 

 markings converge towards the apex of the central triangle, 

 and are parallel to the sides of the lateral thickenings. 



ZONITIDAE 



Guppya molengraaffi, new species 



Type locality: (Cb20) just west of the summit of Sint 

 Christoffclberg, northern Curasao, at an altitude of about 

 1,200 feet. 



