52 University of Michigan 



bosses ; similar to that of the last whorl of grandiensis. Sub- 

 apical whorls (young shells) : similar to those of rupis but with 

 heavier growth-cost ae. Umbilicus: rimate, even smaller than 

 in rupis. Aperture: small, almost circular; with long axis 

 inclined at about 45° to that of shell; internally light orange 

 to chocolate-brown, with white, peristomal callus. Peristome : 

 sharp, interrupted on parietal wall ; not expanded at parietal 

 angle, and with palatal wall slightly emarginate immediately 

 below it; slight expansion of lower palatal and basal regions 

 terminated abruptly just beyond slightly auriculate basal 

 angle ; columellar wall scarcely expanded ; thickened internally 

 by continuous, rounded callus, which is very narrow in the 

 columellar region. 



Operculum (fig. xi-43) : 3I/4 whorls; very similar to that 

 of T. rupis. 



Radula (fig. xi-41) : C/1 ; Ll/l + 1/5-6 ; M/45-47. Inner 

 lateral slightly more attenuate distad and spatulate cusps of 

 outer lateral less variable than in T. megacheilos; other char- 

 acters very similar. 



Measurements 



Shell Aperture Operculum Whorls 



alt. maj.diam. min.diani. alt. diam. long wide 



male 12.4 56(7.0) 46(5.7) 40(5.0) 90(4.5) 30(3.7) 81(3.0) 5 

 female 



(type) 15.8 56(8.9) 48(7.6) 40(6.3) 89(5.6) 34(5.3) 79(4.2) 5 



female 16.4 55(9.0) 48(7.9) 38(6.2) 97(6.0) 31(5.1) 78(4.0) 5^ 



female 17.0 53(9.0) 43(7.2) 37(6.3) 89(5.6) 31(5.3) 79(4.2) 6 

 T. costata; 



fig. (1846- 



1849) 15.7 52(8.2) 44(6.9) 78(5.4) 6 



C17bc. Quite common on both escarpments of Plaja Abau; very com- 

 mon near Seroe Djerimi, between Knip Baai and Plaja Djerimi (165 

 specimens collected). Type lot (see Table V). 



C17a. Quite abundant; this lot is from the top of Seroe Djerimi (128 

 specimens). Somewhat smaller, and with a slightly more noticeable 

 tendency for the spiral sculpture of the last whorl to crenulate the. 

 growth costae. 



C16. Quite abundant (157 specimens). Color and shape similar to 

 typical lot, but would average a trifle larger. Growth costae noticeably 



