Occasional Papers of the Museum of Zoology 63 



sculpture of numerous (19 to 28 counted), regular, compressed, 

 angular ridges, which are more widely spaced on the base than 

 at the sides of the whorl, and heavier and slightly higher than 

 the growth-riblets, which surmount them; intersections de- 

 veloped as very prominent, sharp, pyramidal cusps. Earlier 

 whorls : spiral and growth sculpture weaker and about equal ; 

 distinctly cancellate; cusps at intersections finer, but high 

 and sharp. Subapical whorls : sculpture and shape similar to 

 megacheilos {i.e., apical angle similar to aurantia). Umbili- 

 cus : much larger than in megacheilos, and but little hidden by 

 the peristome. Aperture: inner outline almost circular; in- 

 ternally light buff to dark chocolate, usually with darker, 

 spiral bands. Peristome: roughly triangular and markedly 

 undulate ; parietal angle produced and lobate ; palatal emargi- 

 nation a marked sinus; lower palatal wall extensively devel- 

 oped but scarcely expanded; basal wall abruptly expanded; 

 basal angle flattened; columellar wall auriculate below, but 

 narrowed abruptly a short distance from the parietal wall; 

 internal callus very poorly developed, practically absent on 

 parietal wall. 



Operculum (fig. xi-44) : about 4 whorls; similar to mega- 

 cheilos, but with inner surface (thin, chondroid plate) slightly 

 convex, and outer surface (calcareous plate) deeply and quite 

 regularly concave over its entire surface. 



Eadula : similar to megacheilos. 



Measurements 

 Shell Aperture Operculum Whorls 



alt. maj.diam. niin.diain. alt. diam. long wide 

 male 13.2 85(11.2) 64( 8.5) 61(8.1) 93(7.5) 41(5.4) 80(4.3) 3% 



female 

 (type) 16.0 78(12.4) 63(10.1) 57(9.1) 98(8.9) 39(6.2) 81(5.0) 3% 



Tudora fossor fossor H. Burrington Baker 



(1924; Naut., XXXVII, 94) 



Type locality: (CblTb) valley between Seroes Palomba and 

 Baha Hoendoe, northern Curasao. 



