232 HELIX-OBBA. 



4. Group of H. horizontalis. 



Species with a strong oblique gibbous ridge or swelling a short 

 distance behind the upper lip ; peristome reflexed all around and 

 thickened, preceded by a constriction. The surface is smooth, 

 delicately obliquely striated, 1 to 5 banded. Basal lip toothed or 

 not. Aperture light within. 



H. HORIZONTALIS Pfeiffer. PL 57, figs. 97, 98, 99 (typical); 100, 

 1, (var.) 



Shell umbilicated, depressed, acutely carinated at the periphery, 

 soiled whitish with 3 chestnut bands above (the 3d on the carina), 

 and two below, the outer one at the carina ; inner half of the base 

 of a brown color, lighter than the bands but darker than the ground- 

 color. Aperture horizontal, more than l\ times as wide as long. 

 Basal lip obtusely toothed just within the termination of the basal 

 band. 



Solid, delicately obliquely striated ; spirally banded, the bands 

 continuous, not interrupted by light streaks or blotches ; the third 

 band upon the carina. Apex obtuse. Whorls 4f , flat, the last one 

 suddenly descending at the aperture ; just behind the peristome con- 

 stricted and then having a prominent, oblique gibbous ridge or crest 

 on the upper surface. Aperture oblong, almost horizontal ; peri- 

 stome thickened, convex, reflexed, flesh-colored, continuous ; the 

 upper and basal margins parallel, the basal lip obtusely toothed 

 near its junction with the outer lip. Umbilicus deep, about one- 

 tenth the diam. of the shell. Alt. 13-14, greater diam. 31 mill. 



Island of Batayon and Id. of Tablets, Philippines. 



H. horizontalis PFR. P. Z. S. 1845, p. 40 ; Monographia, i, p. 395 ; 

 Conchylien Cabinet, p. 410, t. 146, f. 14-16. REEVE, Conch. Icon, 

 f. 116. HIDALGO, Journ. de Conchyl. 1887, p. 102. 



The mouth is narrower than in H. reeveana, there is a brown 

 band on the periphery, and the central area of the base is brown. 

 The peripheral keel too is stronger, and the basal lip has an obtuse 

 tooth near its distal extremity. A smaller variety is mentioned by 

 Hidalgo, having three or only two bands, much resembling H. 

 reeveana. It is from Looc, Tablas. 



Var. MAJOR (pi. 57, figs. 100, 1). Decidedly larger than the 

 type, somewhat more depressed, but otherwise identical in colora- 

 tion and proportions. Alt. 13, greater diam. 41, lesser 34 mill. 



